## GdaDataProxy

GdaDataProxy — Proxy to hold modifications for any GdaDataModel, and provides the GdaDataModel interface itself

## Synopsis

                        GdaDataProxy;
                        GdaDataProxyClass;
                        GdaDataProxyPrivate;
    GObject *           gda_data_proxy_new                  (GdaDataModel *model);
    GdaDataModel *      gda_data_proxy_get_proxied_model    (GdaDataProxy *proxy);
    gint                gda_data_proxy_get_proxied_model_n_cols
                                                            (GdaDataProxy *proxy);
    gint                gda_data_proxy_get_proxied_model_n_rows
                                                            (GdaDataProxy *proxy);
    gboolean            gda_data_proxy_is_read_only         (GdaDataProxy *proxy);
    GSList *            gda_data_proxy_get_values           (GdaDataProxy *proxy,
                                                             gint proxy_row,
                                                             gint *cols_index,
                                                             gint n_cols);
    GdaValueAttribute   gda_data_proxy_get_value_attributes (GdaDataProxy *proxy,
                                                             gint proxy_row,
                                                             gint col);
    void                gda_data_proxy_alter_value_attributes
                                                            (GdaDataProxy *proxy,
                                                             gint proxy_row,
                                                             gint col,
                                                             GdaValueAttribute alter_flags);
    gint                gda_data_proxy_get_proxied_model_row
                                                            (GdaDataProxy *proxy,
                                                             gint proxy_row);
    void                gda_data_proxy_delete               (GdaDataProxy *proxy,
                                                             gint proxy_row);
    void                gda_data_proxy_undelete             (GdaDataProxy *proxy,
                                                             gint proxy_row);
    gboolean            gda_data_proxy_row_is_deleted       (GdaDataProxy *proxy,
                                                             gint proxy_row);
    gboolean            gda_data_proxy_row_is_inserted      (GdaDataProxy *proxy,
                                                             gint proxy_row);
    void                gda_data_proxy_cancel_row_changes   (GdaDataProxy *proxy,
                                                             gint proxy_row,
                                                             gint col);
    gboolean            gda_data_proxy_apply_row_changes    (GdaDataProxy *proxy,
                                                             gint proxy_row,
                                                             GError **error);
    gboolean            gda_data_proxy_has_changed          (GdaDataProxy *proxy);
    gboolean            gda_data_proxy_row_has_changed      (GdaDataProxy *proxy,
                                                             gint proxy_row);
    gint                gda_data_proxy_get_n_new_rows       (GdaDataProxy *proxy);
    void                gda_data_proxy_set_sample_size      (GdaDataProxy *proxy,
                                                             gint sample_size);
    gint                gda_data_proxy_get_sample_size      (GdaDataProxy *proxy);
    void                gda_data_proxy_set_sample_start     (GdaDataProxy *proxy,
                                                             gint sample_start);
    gint                gda_data_proxy_get_sample_start     (GdaDataProxy *proxy);
    gint                gda_data_proxy_get_sample_end       (GdaDataProxy *proxy);
    gboolean            gda_data_proxy_apply_all_changes    (GdaDataProxy *proxy,
                                                             GError **error);
    gboolean            gda_data_proxy_cancel_all_changes   (GdaDataProxy *proxy);
    gboolean            gda_data_proxy_set_filter_expr      (GdaDataProxy *proxy,
                                                             const gchar *filter_expr,
                                                             GError **error);
    const gchar *       gda_data_proxy_get_filter_expr      (GdaDataProxy *proxy);
    gint                gda_data_proxy_get_filtered_n_rows  (GdaDataProxy *proxy);

## Object Hierarchy

      GObject
       +----GdaDataProxy

## Implemented Interfaces

GdaDataProxy implements GdaDataModel.

## Properties

      "defer-sync"               gboolean              : Read / Write
      "model"                    GdaDataModel*         : Read / Write / Construct
      "prepend-null-entry"       gboolean              : Read / Write
      "sample-size"              gint                  : Read / Write / Construct

## Signals

      "filter-changed"                                 : Run First
      "row-changes-applied"                            : Run First
      "row-delete-changed"                             : Run First
      "sample-changed"                                 : Run First
      "sample-size-changed"                            : Run First
      "validate-row-changes"                           : Run Last

## Description

This object stores modifications to be made to a GdaDataModel object which is proxied until the modifications are actually written to the GdaDataModel, it can also filter the proxied data model to show only a subset (a defined number of continuous rows or by a filter to apply).

Specifically, for a proxied data model having `nb_cols` columns and `nb_rows` rows, the GdaDataProxy object has the following attributes:

- `2 * nb_cols` columns:

  - the first (>= 0) `nb_cols` columns are the current values stored in the proxy (which correspond to the values of the proxied data model if the considered row has not been changed). The associated values are writable.

  - the last `nb_cols` columns are the values stored in the proxied data model, at column `col - nb_cols`

- a variable number of rows depending on the following attributes:

  - if the proxy is configured to have an empty row as the first row

  - if the proxy only displays parts of the proxied data model

  - if new rows have been added to the proxy

This situation is illustrated in the following schema, where there is a direct mapping between the proxy's rows and the proxied data model's rows:

Note that unless explicitly mentioned, the columns are read-only.

The following figures illustrate row mappings between the data proxy and the proxied data model in several situations (which can be combined, but are shown alone for simplicity):

- situation where rows 1 and 5 have been marked as deleted from the data proxy, using `gda_data_proxy_delete()` method, the data proxy has 2 rows less than the proxied data model:

- situation where the data proxy only shows a sample of the proxied data model at any given time, using the `gda_data_proxy_set_sample_size()` method (the sample here is 4 rows wide, and starts at row 3):

- situation where the data proxy shows a row of NULL values, using the "prepend-null-entry" property:

- situation where a row has been added to the data proxy, using for example the `gda_data_model_append_row()` method:

The GdaDataProxy objects are thread safe, which means any proxy object can be used from any thread at the same time as they implement their own locking mechanisms.

## Details

### GdaDataProxy

    typedef struct _GdaDataProxy GdaDataProxy;

### GdaDataProxyClass

    typedef struct {
    	GObjectClass            parent_class;

    	void                 (* row_delete_changed)   (GdaDataProxy *proxy, gint row, gboolean to_be_deleted);

    	void                 (* sample_size_changed)  (GdaDataProxy *proxy, gint sample_size);
    	void                 (* sample_changed)       (GdaDataProxy *proxy, gint sample_start, gint sample_end);

    	GError              *(* validate_row_changes) (GdaDataProxy *proxy, gint row, gint proxied_row);
    	void                 (* row_changes_applied)  (GdaDataProxy *proxy, gint row, gint proxied_row);

    	void                 (* filter_changed)       (GdaDataProxy *proxy);

    	/* Padding for future expansion */
    	void (*_gda_reserved1) (void);
    	void (*_gda_reserved2) (void);
    	void (*_gda_reserved3) (void);
    	void (*_gda_reserved4) (void);
    } GdaDataProxyClass;

### GdaDataProxyPrivate

    typedef struct _GdaDataProxyPrivate GdaDataProxyPrivate;

### gda_data_proxy_new ()

    GObject *           gda_data_proxy_new                  (GdaDataModel *model);

Creates a new proxy for `model`

`model` : | Data model to be proxied. [transfer none]
Returns : | a new GdaDataProxy object. [transfer full]

### gda_data_proxy_get_proxied_model ()

    GdaDataModel *      gda_data_proxy_get_proxied_model    (GdaDataProxy *proxy);

Fetch the GdaDataModel which `proxy` does proxy

`proxy` : | a GdaDataProxy object
Returns : | the proxied data model. [transfer none]

### gda_data_proxy_get_proxied_model_n_cols ()

    gint                gda_data_proxy_get_proxied_model_n_cols
                                                            (GdaDataProxy *proxy);

Get the number of columns in the proxied data model

`proxy` : | a GdaDataProxy object
Returns : | the number of columns, or -1 if an error occurred

### gda_data_proxy_get_proxied_model_n_rows ()

    gint                gda_data_proxy_get_proxied_model_n_rows
                                                            (GdaDataProxy *proxy);

Get the number of rows in the proxied data model

`proxy` : | a GdaDataProxy object
Returns : | the number of rows, or -1 if the number of rows is not known

### gda_data_proxy_is_read_only ()

    gboolean            gda_data_proxy_is_read_only         (GdaDataProxy *proxy);

`proxy` : | a GdaDataProxy object
Returns : | TRUE if the proxied data model is itself read-only

### gda_data_proxy_get_values ()

    GSList *            gda_data_proxy_get_values           (GdaDataProxy *proxy,
                                                             gint proxy_row,
                                                             gint *cols_index,
                                                             gint n_cols);

Retrieve a whole list of values from the `proxy` data model. This function calls `gda_data_proxy_get_value()` for each column index specified in `cols_index`, and generates a GSList on the way.

`proxy` : | a GdaDataProxy object
`proxy_row` : | a proxy row
`cols_index` : | array containing the columns for which the values are requested. [array][array length=n_cols]
`n_cols` : | size of `cols_index`
Returns : | a new list of values (the list must be freed, not the values), or `NULL` if an error occurred. [element-type GValue][transfer container GValue]

### gda_data_proxy_get_value_attributes ()

    GdaValueAttribute   gda_data_proxy_get_value_attributes (GdaDataProxy *proxy,
                                                             gint proxy_row,
                                                             gint col);

Get the attributes of the value stored at (proxy_row, col) in `proxy`, which is an ORed value of GdaValueAttribute flags

`proxy` : | a GdaDataProxy object
`proxy_row` : | a proxy row
`col` : | a valid proxy column
Returns : | the attribute. [transfer none]

### gda_data_proxy_alter_value_attributes ()

    void                gda_data_proxy_alter_value_attributes
                                                            (GdaDataProxy *proxy,
                                                             gint proxy_row,
                                                             gint col,
                                                             GdaValueAttribute alter_flags);

Alters the attributes of the value stored at (proxy_row, col) in `proxy`. the `alter_flags` can only contain the GDA_VALUE_ATTR_IS_NULL, GDA_VALUE_ATTR_IS_DEFAULT and GDA_VALUE_ATTR_IS_UNCHANGED flags (other flags are ignored).

`proxy` : | a GdaDataProxy object
`proxy_row` : | A proxy row number
`col` : | a valid column number
`alter_flags` : | flags to alter the attributes. [transfer none]

### gda_data_proxy_get_proxied_model_row ()

    gint                gda_data_proxy_get_proxied_model_row
                                                            (GdaDataProxy *proxy,
                                                             gint proxy_row);

Get the `proxy`'s proxied model row corresponding to `proxy_row`

`proxy` : | a GdaDataProxy object
`proxy_row` : | A proxy row number
Returns : | the proxied model's row, or -1 if `proxy` row which only exists `proxy`

### gda_data_proxy_delete ()

    void                gda_data_proxy_delete               (GdaDataProxy *proxy,
                                                             gint proxy_row);

Marks the row `proxy_row` to be deleted

`proxy` : | a GdaDataProxy object
`proxy_row` : | A proxy row number

### gda_data_proxy_undelete ()

    void                gda_data_proxy_undelete             (GdaDataProxy *proxy,
                                                             gint proxy_row);

Remove the "to be deleted" mark at the row `proxy_row`, if it existed.

`proxy` : | a GdaDataProxy object
`proxy_row` : | A proxy row number

### gda_data_proxy_row_is_deleted ()

    gboolean            gda_data_proxy_row_is_deleted       (GdaDataProxy *proxy,
                                                             gint proxy_row);

Tells if the row number `proxy_row` is marked to be deleted.

`proxy` : | a GdaDataProxy object
`proxy_row` : | A proxy row number
Returns : | TRUE if the row is marked to be deleted

### gda_data_proxy_row_is_inserted ()

    gboolean            gda_data_proxy_row_is_inserted      (GdaDataProxy *proxy,
                                                             gint proxy_row);

Tells if the row number `proxy_row` is a row which has been inserted in `proxy` (and is thus not in the proxied data model).

`proxy` : | a GdaDataProxy object
`proxy_row` : | A proxy row number
Returns : | TRUE if the row is an inserted row

### gda_data_proxy_cancel_row_changes ()

    void                gda_data_proxy_cancel_row_changes   (GdaDataProxy *proxy,
                                                             gint proxy_row,
                                                             gint col);

Resets data at the corresponding row and column. If `proxy_row` corresponds to a new row, then that new row is deleted from `proxy`.

`proxy` : | a GdaDataProxy object
`proxy_row` : | the row to cancel changes
`col` : | the column to cancel changes, or less than 0 to cancel any change on the `row` row

### gda_data_proxy_apply_row_changes ()

    gboolean            gda_data_proxy_apply_row_changes    (GdaDataProxy *proxy,
                                                             gint proxy_row,
                                                             GError **error);

Commits the modified data in the proxy back into the GdaDataModel.

`proxy` : | a GdaDataProxy object
`proxy_row` : | the row number to commit
`error` : | place to store the error, or `NULL`
Returns : | TRUE if no error occurred.

### gda_data_proxy_has_changed ()

    gboolean            gda_data_proxy_has_changed          (GdaDataProxy *proxy);

Tells if `proxy` contains any modifications not applied to the proxied data model.

`proxy` : | a GdaDataProxy object
Returns : | TRUE if there are some modifications in `proxy`

### gda_data_proxy_row_has_changed ()

    gboolean            gda_data_proxy_row_has_changed      (GdaDataProxy *proxy,
                                                             gint proxy_row);

Tells if the row number `proxy_row` has changed

`proxy` : | a GdaDataProxy object
`proxy_row` : | A proxy row number
Returns : | TRUE if the row has changed

### gda_data_proxy_get_n_new_rows ()

    gint                gda_data_proxy_get_n_new_rows       (GdaDataProxy *proxy);

Get the number of rows which have been added to `proxy` and which are not part of the proxied data model.

`proxy` : | a GdaDataProxy object
Returns : | the number of new rows

### gda_data_proxy_set_sample_size ()

    void                gda_data_proxy_set_sample_size      (GdaDataProxy *proxy,
                                                             gint sample_size);

Sets the size of each chunk of data to display: the maximum number of rows which can be "displayed" at a time (the maximum number of rows which `proxy` pretends to have). The default value is arbitrary 300 as it is big enough to be able to display quite a lot of data, but small enough to avoid too much data displayed at the same time.

Note: the rows which have been added but not yet committed will always be displayed regardless of the current chunk of data, and the modified rows which are not visible when the displayed chunk of data changes are still held as modified rows.

To remove the chunking of the data to display, simply pass `sample_size` the `0` value.

`proxy` : | a GdaDataProxy object
`sample_size` : | the requested size of a chunk, or 0

### gda_data_proxy_get_sample_size ()

    gint                gda_data_proxy_get_sample_size      (GdaDataProxy *proxy);

Get the size of each chunk of data displayed at a time.

`proxy` : | a GdaDataProxy object
Returns : | the chunk (or sample) size, or 0 if chunking is disabled.

### gda_data_proxy_set_sample_start ()

    void                gda_data_proxy_set_sample_start     (GdaDataProxy *proxy,
                                                             gint sample_start);

Sets the number of the first row to be available in `proxy` (in reference to the proxied data model)

`proxy` : | a GdaDataProxy object
`sample_start` : | the number of the first row to be displayed

### gda_data_proxy_get_sample_start ()

    gint                gda_data_proxy_get_sample_start     (GdaDataProxy *proxy);

Get the number of the first row to be available in `proxy` (in reference to the proxied data model)

`proxy` : | a GdaDataProxy object
Returns : | the number of the first proxied model's row.

### gda_data_proxy_get_sample_end ()

    gint                gda_data_proxy_get_sample_end       (GdaDataProxy *proxy);

Get the number of the last row to be available in `proxy` (in reference to the proxied data model)

`proxy` : | a GdaDataProxy object
Returns : | the number of the last proxied model's row.

### gda_data_proxy_apply_all_changes ()

    gboolean            gda_data_proxy_apply_all_changes    (GdaDataProxy *proxy,
                                                             GError **error);

Apply all the changes stored in the proxy to the proxied data model. The changes are done row after row, and if an error occurs, then it is possible that not all the changes to all the rows have been applied.

`proxy` : | a GdaDataProxy object
`error` : | a place to store errors, or `NULL`
Returns : | TRUE if no error occurred

### gda_data_proxy_cancel_all_changes ()

    gboolean            gda_data_proxy_cancel_all_changes   (GdaDataProxy *proxy);

Cancel all the changes stored in the proxy (the `proxy` will be reset to its state as it was just after creation).

`proxy` : | a GdaDataProxy object
Returns : | TRUE if no error occurred

### gda_data_proxy_set_filter_expr ()

    gboolean            gda_data_proxy_set_filter_expr      (GdaDataProxy *proxy,
                                                             const gchar *filter_expr,
                                                             GError **error);

Sets a filter among the rows presented by `proxy`. The filter is defined by a filter expression which can be any SQL valid expression using `proxy`'s columns. For instance if `proxy` has the "id" and "name" columns, then a filter can be "length(name) < 5" to filter only the rows where the length of the name is strictly inferior to 5, or "id >= 1000 and id < 2000 order by name limit 50" to filter only the rows where the id is between 1000 and 2000, ordered by name and limited to 50 rows.

Note about column names: real column names can be used (double quoted if necessary), but columns can also be named "_<column number>" with column numbers starting at 1.

Note that any previous filter expression is replaced with the new `filter_expr` if no error occurs (if an error occurs, then any previous filter is left unchanged).

`proxy` : | a GdaDataProxy object
`filter_expr` : | an SQL based expression which will filter the contents of `proxy`, or `NULL` to remove any previous filter
`error` : | a place to store errors, or `NULL`
Returns : | TRUE if no error occurred

### gda_data_proxy_get_filter_expr ()

    const gchar *       gda_data_proxy_get_filter_expr      (GdaDataProxy *proxy);

Get the current filter expression used by `proxy`.

`proxy` : | a GdaDataProxy object
Returns : | the current filter expression or `NULL` if no filter has been set

### gda_data_proxy_get_filtered_n_rows ()

    gint                gda_data_proxy_get_filtered_n_rows  (GdaDataProxy *proxy);

Get the total number of filtered rows in `proxy` if a filter has been applied. As new rows (rows added to the proxy and not yet added to the proxied data model) and rows to remove (rows marked for removal but not yet removed from the proxied data model) are also filtered, the returned number also contains references to new rows and rows to be removed.

`proxy` : | a GdaDataProxy object
Returns : | the number of filtered rows in `proxy`, or -1 if no filter has been applied

## Property Details

### The `"defer-sync"` property

      "defer-sync"               gboolean              : Read / Write

Tells if changes to the sample of rows displayed is done in background in several steps or if it's done in one step.

Default value: TRUE

### The `"model"` property

      "model"                    GdaDataModel*         : Read / Write / Construct

Proxied data model.

### The `"prepend-null-entry"` property

      "prepend-null-entry"       gboolean              : Read / Write

Tells if a row composed of NULL values is inserted as the proxy's first row.

Default value: FALSE

### The `"sample-size"` property

      "sample-size"              gint                  : Read / Write / Construct

Number of rows which the proxy will contain at any time, like a sliding window on the proxied data model.

Allowed values: [0,2147483646]

Default value: 300

## Signal Details

### The `"filter-changed"` signal

    void                user_function                      (GdaDataProxy *proxy,
                                                            gpointer      user_data)      : Run First

Gets emitted when `proxy`'s filter has been changed

@:

`proxy` : | the GdaDataProxy
`user_data` : | user data set when the signal handler was connected.

### The `"row-changes-applied"` signal

    void                user_function                      (GdaDataProxy *proxy,
                                                            gint          row,
                                                            gint          proxied_row,
                                                            gpointer      user_data)        : Run First

Gets emitted when `proxy` has committed a row change to the proxied data model.

@: @: @:

`proxy` : | the GdaDataProxy
`row` : | the proxy's row
`proxied_row` : | the proxied data model's row
`user_data` : | user data set when the signal handler was connected.

### The `"row-delete-changed"` signal

    void                user_function                      (GdaDataProxy *proxy,
                                                            gint          row,
                                                            gboolean      to_be_deleted,
                                                            gpointer      user_data)          : Run First

Gets emitted whenever a row has been marked to be deleted, or has been unmarked to be deleted

@: @: @:

`proxy` : | the GdaDataProxy
`row` : | the concerned `proxy`'s row
`to_be_deleted` : | tells if the `row` is marked to be deleted
`user_data` : | user data set when the signal handler was connected.

### The `"sample-changed"` signal

    void                user_function                      (GdaDataProxy *proxy,
                                                            gint          sample_start,
                                                            gint          sample_end,
                                                            gpointer      user_data)         : Run First

Gets emitted whenever `proxy`'s sample size has been changed. `sample_start` and `sample_end` are in reference to the proxied data model.

@: @: @:

`proxy` : | the GdaDataProxy
`sample_start` : | the first row of the sample
`sample_end` : | the last row of the sample
`user_data` : | user data set when the signal handler was connected.

### The `"sample-size-changed"` signal

    void                user_function                      (GdaDataProxy *proxy,
                                                            gint          sample_size,
                                                            gpointer      user_data)        : Run First

Gets emitted whenever `proxy`'s sample size has been changed

@: @:

`proxy` : | the GdaDataProxy
`sample_size` : | the new sample size
`user_data` : | user data set when the signal handler was connected.

### The `"validate-row-changes"` signal

    GdaError*           user_function                      (GdaDataProxy *proxy,
                                                            gint          row,
                                                            gint          proxied_row,
                                                            gpointer      user_data)        : Run Last

Gets emitted when `proxy` is about to commit a row change to the proxied data model. If any callback returns a non `NULL` value, then the change commit fails with the returned GError

@: @: @:

`proxy` : | the GdaDataProxy
`row` : | the proxy's row
`proxied_row` : | the proxied data model's row
`user_data` : | user data set when the signal handler was connected.
Returns : | a new GError if validation failed, or `NULL`