GtkCellAreaContext

## GtkCellAreaContext GtkCellAreaContext — Stores geometrical information for a series of rows in a GtkCellArea |

## Synopsis

    #include <gtk/gtk.h>

    struct              GtkCellAreaContextClass;
                        GtkCellAreaContext;
    GtkCellArea *       gtk_cell_area_context_get_area      (GtkCellAreaContext *context);
    void                gtk_cell_area_context_allocate      (GtkCellAreaContext *context,
                                                             gint width,
                                                             gint height);
    void                gtk_cell_area_context_reset         (GtkCellAreaContext *context);
    void                gtk_cell_area_context_get_preferred_width
                                                            (GtkCellAreaContext *context,
                                                             gint *minimum_width,
                                                             gint *natural_width);
    void                gtk_cell_area_context_get_preferred_height
                                                            (GtkCellAreaContext *context,
                                                             gint *minimum_height,
                                                             gint *natural_height);
    void                gtk_cell_area_context_get_preferred_height_for_width
                                                            (GtkCellAreaContext *context,
                                                             gint width,
                                                             gint *minimum_height,
                                                             gint *natural_height);
    void                gtk_cell_area_context_get_preferred_width_for_height
                                                            (GtkCellAreaContext *context,
                                                             gint height,
                                                             gint *minimum_width,
                                                             gint *natural_width);
    void                gtk_cell_area_context_get_allocation
                                                            (GtkCellAreaContext *context,
                                                             gint *width,
                                                             gint *height);
    void                gtk_cell_area_context_push_preferred_width
                                                            (GtkCellAreaContext *context,
                                                             gint minimum_width,
                                                             gint natural_width);
    void                gtk_cell_area_context_push_preferred_height
                                                            (GtkCellAreaContext *context,
                                                             gint minimum_height,
                                                             gint natural_height);

## Object Hierarchy

      GObject
       +----GtkCellAreaContext

## Properties

      "area"                     GtkCellArea*          : Read / Write / Construct Only
      "minimum-height"           gint                  : Read
      "minimum-width"            gint                  : Read
      "natural-height"           gint                  : Read
      "natural-width"            gint                  : Read

## Description

The GtkCellAreaContext object is created by a given GtkCellArea implementation via its `GtkCellAreaClass.create_context()` virtual method and is used to store cell sizes and alignments for a series of GtkTreeModel rows that are requested and rendered in the same context.

GtkCellLayout widgets can create any number of contexts in which to request and render groups of data rows. However its important that the same context which was used to request sizes for a given GtkTreeModel row also be used for the same row when calling other GtkCellArea APIs such as `gtk_cell_area_render()` and `gtk_cell_area_event()`.

## Details

### struct GtkCellAreaContextClass

    struct GtkCellAreaContextClass {
      void    (* allocate)                       (GtkCellAreaContext *context,
                                                  gint                width,
                                                  gint                height);
      void    (* reset)                          (GtkCellAreaContext *context);
      void    (* get_preferred_height_for_width) (GtkCellAreaContext *context,
                                                  gint                width,
                                                  gint               *minimum_height,
                                                  gint               *natural_height);
      void    (* get_preferred_width_for_height) (GtkCellAreaContext *context,
                                                  gint                height,
                                                  gint               *minimum_width,
                                                  gint               *natural_width);
    };

`allocate` () | This tells the context that an allocation width or height (or both) have been decided for a group of rows. The context should store any allocations for internally aligned cells at this point so that they dont need to be recalculated at `gtk_cell_area_render()` time.
`reset` () | Clear any previously stored information about requested and allocated sizes for the context.
`get_preferred_height_for_width` () | Returns the aligned height for the given width that context must store while collecting sizes for it's rows.
`get_preferred_width_for_height` () | Returns the aligned width for the given height that context must store while collecting sizes for it's rows.

### GtkCellAreaContext

    typedef struct _GtkCellAreaContext GtkCellAreaContext;

### gtk_cell_area_context_get_area ()

    GtkCellArea *       gtk_cell_area_context_get_area      (GtkCellAreaContext *context);

Fetches the GtkCellArea this `context` was created by.

This is generally unneeded by layouting widgets; however it is important for the context implementation itself to fetch information about the area it is being used for.

For instance at `GtkCellAreaContextClass.allocate()` time its important to know details about any cell spacing that the GtkCellArea is configured with in order to compute a proper allocation.

`context` : | a GtkCellAreaContext
Returns : | the GtkCellArea this context was created by. [transfer none]

Since 3.0

### gtk_cell_area_context_allocate ()

    void                gtk_cell_area_context_allocate      (GtkCellAreaContext *context,
                                                             gint width,
                                                             gint height);

Allocates a width and/or a height for all rows which are to be rendered with `context`.

Usually allocation is performed only horizontally or sometimes vertically since a group of rows are usually rendered side by side vertically or horizontally and share either the same width or the same height. Sometimes they are allocated in both horizontal and vertical orientations producing a homogeneous effect of the rows. This is generally the case for GtkTreeView when "fixed-height-mode" is enabled.

Since 3.0

`context` : | a GtkCellAreaContext
`width` : | the allocated width for all GtkTreeModel rows rendered with `context`, or -1.
`height` : | the allocated height for all GtkTreeModel rows rendered with `context`, or -1.

### gtk_cell_area_context_reset ()

    void                gtk_cell_area_context_reset         (GtkCellAreaContext *context);

Resets any previously cached request and allocation data.

When underlying GtkTreeModel data changes its important to reset the context if the content size is allowed to shrink. If the content size is only allowed to grow (this is usually an option for views rendering large data stores as a measure of optimization), then only the row that changed or was inserted needs to be (re)requested with `gtk_cell_area_get_preferred_width()`.

When the new overall size of the context requires that the allocated size changes (or whenever this allocation changes at all), the variable row sizes need to be re-requested for every row.

For instance, if the rows are displayed all with the same width from top to bottom then a change in the allocated width necessitates a recalculation of all the displayed row heights using `gtk_cell_area_get_preferred_height_for_width()`.

Since 3.0

`context` : | a GtkCellAreaContext

### gtk_cell_area_context_get_preferred_width ()

    void                gtk_cell_area_context_get_preferred_width
                                                            (GtkCellAreaContext *context,
                                                             gint *minimum_width,
                                                             gint *natural_width);

Gets the accumulative preferred width for all rows which have been requested with this context.

After `gtk_cell_area_context_reset()` is called and/or before ever requesting the size of a GtkCellArea, the returned values are 0.

`context` : | a GtkCellAreaContext
`minimum_width` : | location to store the minimum width, or `NULL`. [out][allow-none]
`natural_width` : | location to store the natural width, or `NULL`. [out][allow-none]

Since 3.0

### gtk_cell_area_context_get_preferred_height ()

    void                gtk_cell_area_context_get_preferred_height
                                                            (GtkCellAreaContext *context,
                                                             gint *minimum_height,
                                                             gint *natural_height);

Gets the accumulative preferred height for all rows which have been requested with this context.

After `gtk_cell_area_context_reset()` is called and/or before ever requesting the size of a GtkCellArea, the returned values are 0.

`context` : | a GtkCellAreaContext
`minimum_height` : | location to store the minimum height, or `NULL`. [out][allow-none]
`natural_height` : | location to store the natural height, or `NULL`. [out][allow-none]

Since 3.0

### gtk_cell_area_context_get_preferred_height_for_width ()

    void                gtk_cell_area_context_get_preferred_height_for_width
                                                            (GtkCellAreaContext *context,
                                                             gint width,
                                                             gint *minimum_height,
                                                             gint *natural_height);

Gets the accumulative preferred height for `width` for all rows which have been requested for the same said `width` with this context.

After `gtk_cell_area_context_reset()` is called and/or before ever requesting the size of a GtkCellArea, the returned values are -1.

`context` : | a GtkCellAreaContext
`width` : | a proposed width for allocation
`minimum_height` : | location to store the minimum height, or `NULL`. [out][allow-none]
`natural_height` : | location to store the natural height, or `NULL`. [out][allow-none]

Since 3.0

### gtk_cell_area_context_get_preferred_width_for_height ()

    void                gtk_cell_area_context_get_preferred_width_for_height
                                                            (GtkCellAreaContext *context,
                                                             gint height,
                                                             gint *minimum_width,
                                                             gint *natural_width);

Gets the accumulative preferred width for `height` for all rows which have been requested for the same said `height` with this context.

After `gtk_cell_area_context_reset()` is called and/or before ever requesting the size of a GtkCellArea, the returned values are -1.

`context` : | a GtkCellAreaContext
`height` : | a proposed height for allocation
`minimum_width` : | location to store the minimum width, or `NULL`. [out][allow-none]
`natural_width` : | location to store the natural width, or `NULL`. [out][allow-none]

Since 3.0

### gtk_cell_area_context_get_allocation ()

    void                gtk_cell_area_context_get_allocation
                                                            (GtkCellAreaContext *context,
                                                             gint *width,
                                                             gint *height);

Fetches the current allocation size for `context`.

If the context was not allocated in width or height, or if the context was recently reset with `gtk_cell_area_context_reset()`, the returned value will be -1.

`context` : | a GtkCellAreaContext
`width` : | location to store the allocated width, or `NULL`. [out][allow-none]
`height` : | location to store the allocated height, or `NULL`. [out][allow-none]

Since 3.0

### gtk_cell_area_context_push_preferred_width ()

    void                gtk_cell_area_context_push_preferred_width
                                                            (GtkCellAreaContext *context,
                                                             gint minimum_width,
                                                             gint natural_width);

Causes the minimum and/or natural width to grow if the new proposed sizes exceed the current minimum and natural width.

This is used by GtkCellAreaContext implementations during the request process over a series of GtkTreeModel rows to progressively push the requested width over a series of `gtk_cell_area_get_preferred_width()` requests.

`context` : | a GtkCellAreaContext
`minimum_width` : | the proposed new minimum width for `context`
`natural_width` : | the proposed new natural width for `context`

Since 3.0

### gtk_cell_area_context_push_preferred_height ()

    void                gtk_cell_area_context_push_preferred_height
                                                            (GtkCellAreaContext *context,
                                                             gint minimum_height,
                                                             gint natural_height);

Causes the minimum and/or natural height to grow if the new proposed sizes exceed the current minimum and natural height.

This is used by GtkCellAreaContext implementations during the request process over a series of GtkTreeModel rows to progressively push the requested height over a series of `gtk_cell_area_get_preferred_height()` requests.

`context` : | a GtkCellAreaContext
`minimum_height` : | the proposed new minimum height for `context`
`natural_height` : | the proposed new natural height for `context`

Since 3.0

## Property Details

### The `"area"` property

      "area"                     GtkCellArea*          : Read / Write / Construct Only

The GtkCellArea this context was created by

Since 3.0

### The `"minimum-height"` property

      "minimum-height"           gint                  : Read

The minimum height for the GtkCellArea in this context for all GtkTreeModel rows that this context was requested for using `gtk_cell_area_get_preferred_height()`.

Allowed values: >= G_MAXULONG

Default value: -1

Since 3.0

### The `"minimum-width"` property

      "minimum-width"            gint                  : Read

The minimum width for the GtkCellArea in this context for all GtkTreeModel rows that this context was requested for using `gtk_cell_area_get_preferred_width()`.

Allowed values: >= G_MAXULONG

Default value: -1

Since 3.0

### The `"natural-height"` property

      "natural-height"           gint                  : Read

The natural height for the GtkCellArea in this context for all GtkTreeModel rows that this context was requested for using `gtk_cell_area_get_preferred_height()`.

Allowed values: >= G_MAXULONG

Default value: -1

Since 3.0

### The `"natural-width"` property

      "natural-width"            gint                  : Read

The natural width for the GtkCellArea in this context for all GtkTreeModel rows that this context was requested for using `gtk_cell_area_get_preferred_width()`.

Allowed values: >= G_MAXULONG

Default value: -1

Since 3.0