framebuffer: Add dither_enabled getter/setters

This adds a getter and setter for requesting dithering to be enabled.

Dithering is a hardware dependent technique to increase the visible
color resolution beyond what the underlying hardware supports by playing
tricks with the colors placed into the framebuffer to give the illusion
of other colors. (For example this can be compared to half-toning used
by some news papers to show varying levels of grey even though their may
only be black and white are available).

The results of enabling dithering are platform dependent and may have no
effect.

Signed-off-by: Neil Roberts <neil@linux.intel.com>
This commit is contained in:
Robert Bragg 2011-07-13 16:33:25 +01:00
parent ee4adeff4a
commit 3ed8c8d0ba
5 changed files with 75 additions and 0 deletions

View File

@ -203,6 +203,8 @@ struct _CoglContext
CoglPipelineProgramType current_vertex_program_type;
GLuint current_gl_program;
gboolean current_gl_dither_enabled;
/* List of types that will be considered a subclass of CoglTexture in
cogl_is_texture */
GSList *texture_types;

View File

@ -276,6 +276,8 @@ cogl_context_new (CoglDisplay *display,
context->current_vertex_program_type = COGL_PIPELINE_PROGRAM_TYPE_FIXED;
context->current_gl_program = 0;
context->current_gl_dither_enabled = TRUE;
context->gl_blend_enable_cache = FALSE;
context->depth_test_enabled_cache = FALSE;

View File

@ -74,6 +74,8 @@ struct _CoglFramebuffer
int green_bits;
int alpha_bits;
gboolean dither_enabled;
/* We journal the textured rectangles we want to submit to OpenGL so
* we have an oppertunity to batch them together into less draw
* calls. */

View File

@ -148,6 +148,7 @@ _cogl_framebuffer_init (CoglFramebuffer *framebuffer,
framebuffer->viewport_y = 0;
framebuffer->viewport_width = width;
framebuffer->viewport_height = height;
framebuffer->dither_enabled = TRUE;
framebuffer->modelview_stack = _cogl_matrix_stack_new ();
framebuffer->projection_stack = _cogl_matrix_stack_new ();
@ -1436,6 +1437,15 @@ _cogl_framebuffer_flush_state (CoglFramebuffer *draw_buffer,
_cogl_framebuffer_init_bits (draw_buffer);
_cogl_framebuffer_init_bits (read_buffer);
if (ctx->current_gl_dither_enabled != draw_buffer->dither_enabled)
{
if (draw_buffer->dither_enabled)
GE (ctx, glEnable (GL_DITHER));
else
GE (ctx, glDisable (GL_DITHER));
ctx->current_gl_dither_enabled = draw_buffer->dither_enabled;
}
/* XXX: Flushing clip state may trash the modelview and projection
* matrices so we must do it before flushing the matrices...
*/
@ -1482,6 +1492,23 @@ cogl_framebuffer_get_alpha_bits (CoglFramebuffer *framebuffer)
return framebuffer->alpha_bits;
}
gboolean
cogl_framebuffer_get_dither_enabled (CoglFramebuffer *framebuffer)
{
return framebuffer->dither_enabled;
}
void
cogl_framebuffer_set_dither_enabled (CoglFramebuffer *framebuffer,
gboolean dither_enabled)
{
if (framebuffer->dither_enabled == dither_enabled)
return;
cogl_flush (); /* Currently dithering changes aren't tracked in the journal */
framebuffer->dither_enabled = dither_enabled;
}
gboolean
_cogl_framebuffer_try_fast_read_pixel (CoglFramebuffer *framebuffer,
int x,

View File

@ -185,6 +185,48 @@ cogl_framebuffer_get_blue_bits (CoglFramebuffer *framebuffer);
int
cogl_framebuffer_get_alpha_bits (CoglFramebuffer *framebuffer);
/**
* cogl_framebuffer_get_dither_enabled:
* @framebuffer: a pointer to a #CoglFramebuffer
*
* Returns whether dithering has been requested for the given @framebuffer.
* See cogl_framebuffer_set_dither_enabled() for more details about dithering.
*
* <note>This may return %TRUE even when the underlying @framebuffer
* display pipeline does not support dithering. This value only represents
* the user's request for dithering.</note>
*
* Return value: %TRUE if dithering has been requested or %FALSE if not.
*/
gboolean
cogl_framebuffer_get_dither_enabled (CoglFramebuffer *framebuffer);
/**
* cogl_framebuffer_set_dither_enabled:
* @framebuffer: a pointer to a #CoglFramebuffer
* @dither_enabled: %TRUE to enable dithering or %FALSE to disable
*
* Enables or disabled dithering if supported by the hardware.
*
* Dithering is a hardware dependent technique to increase the visible
* color resolution beyond what the underlying hardware supports by playing
* tricks with the colors placed into the framebuffer to give the illusion
* of other colors. (For example this can be compared to half-toning used
* by some news papers to show varying levels of grey even though their may
* only be black and white are available).
*
* If the current display pipeline for @framebuffer does not support dithering
* then this has no affect.
*
* Dithering is enabled by default.
*
* Since: 1.8
* Stability: unstable
*/
void
cogl_framebuffer_set_dither_enabled (CoglFramebuffer *framebuffer,
gboolean dither_enabled);
#define cogl_framebuffer_swap_buffers cogl_framebuffer_swap_buffers_EXP
void
cogl_framebuffer_swap_buffers (CoglFramebuffer *framebuffer);