[cairo] [PATCH 2/3] Support a different pixel format for HDC

[LRN]

Add cairo API to set up a Win32 surface for an HDC with an alpha channel.

Signed-off-by: Bas Schouten <bas.schouten at live.nl>
---
 src/cairo-win32.h                       |  3 ++
 src/win32/cairo-win32-display-surface.c | 64 ++++++++++++++++++++++-----------
 2 files changed, 47 insertions(+), 21 deletions(-)

diff --git a/src/cairo-win32.h b/src/cairo-win32.h
index 3d2e1c6..2dd8934 100644
--- a/src/cairo-win32.h
+++ b/src/cairo-win32.h
@@ -49,6 +49,9 @@ cairo_public cairo_surface_t *
 cairo_win32_surface_create (HDC hdc);

 cairo_public cairo_surface_t *
+cairo_win32_surface_create_with_alpha (HDC hdc);
+
+cairo_public cairo_surface_t *
 cairo_win32_printing_surface_create (HDC hdc);

 cairo_public cairo_surface_t *
diff --git a/src/win32/cairo-win32-display-surface.c b/src/win32/cairo-win32-display-surface.c
index 965f2c4..d002ce2 100644
--- a/src/win32/cairo-win32-display-surface.c
+++ b/src/win32/cairo-win32-display-surface.c
@@ -916,33 +916,14 @@ static const cairo_surface_backend_t cairo_win32_display_surface_backend = {
  *              multiplied by all the src components.
  */

-/**
- * cairo_win32_surface_create:
- * @hdc: the DC to create a surface for
- *
- * Creates a cairo surface that targets the given DC.  The DC will be
- * queried for its initial clip extents, and this will be used as the
- * size of the cairo surface.  The resulting surface will always be of
- * format %CAIRO_FORMAT_RGB24; should you need another surface format,
- * you will need to create one through
- * cairo_win32_surface_create_with_dib().
- *
- * Return value: the newly created surface
- *
- * Since: 1.0
- **/
-cairo_surface_t *
-cairo_win32_surface_create (HDC hdc)
+static cairo_surface_t *
+cairo_win32_surface_create_internal (HDC hdc, cairo_format_t format)
 {
     cairo_win32_display_surface_t *surface;

-    cairo_format_t format;
     cairo_status_t status;
     cairo_device_t *device;

-    /* Assume that everything coming in as a HDC is RGB24 */
-    format = CAIRO_FORMAT_RGB24;
-
     surface = malloc (sizeof (*surface));
     if (surface == NULL)
 	return _cairo_surface_create_in_error (_cairo_error (CAIRO_STATUS_NO_MEMORY));
@@ -977,6 +958,48 @@ cairo_win32_surface_create (HDC hdc)
 }

 /**
+ * cairo_win32_surface_create:
+ * @hdc: the DC to create a surface for
+ *
+ * Creates a cairo surface that targets the given DC.  The DC will be
+ * queried for its initial clip extents, and this will be used as the
+ * size of the cairo surface.  The resulting surface will always be of
+ * format %CAIRO_FORMAT_RGB24; should you need another surface format,
+ * you will need to create one through
+ * cairo_win32_surface_create_with_dib() or call
+ * cairo_win32_surface_create_with_alpha().
+ *
+ * Return value: the newly created surface
+ *
+ * Since: 1.0
+ **/
+cairo_surface_t *
+cairo_win32_surface_create (HDC hdc)
+{
+    return cairo_win32_surface_create_internal(hdc, CAIRO_FORMAT_RGB24);
+}
+
+/**
+ * cairo_win32_surface_create_with_alpha:
+ * @hdc: the DC to create a surface for
+ *
+ * Creates a cairo surface that targets the given DC.  The DC will be
+ * queried for its initial clip extents, and this will be used as the
+ * size of the cairo surface.  The resulting surface will always be of
+ * format %CAIRO_FORMAT_ARGB32 (as supported for transparent windows with
+ * Windows Vista and up).
+ *
+ * Return value: the newly created surface
+ *
+ * Since: 1.12
+ **/
+cairo_surface_t *
+cairo_win32_surface_create_with_alpha (HDC hdc)
+{
+    return cairo_win32_surface_create_internal(hdc, CAIRO_FORMAT_ARGB32);
+}
+
+/**
  * cairo_win32_surface_create_with_dib:
  * @format: format of pixels in the surface to create
  * @width: width of the surface, in pixels
-- 
1.8.5.3