[Glamor] [PATCH 1/3] Use glDrawRangeElements instead of glDrawElements

[Grigori Goronzy]

This lets us explicitly specify the range of vertices that are used,
which the OpenGL driver can use for optimization. Particularly,
it results in lower CPU overhead with Mesa-based drivers.
---
 src/glamor_fill.c        | 9 +++++++++
 src/glamor_gl_dispatch.c | 1 +
 src/glamor_gl_dispatch.h | 1 +
 src/glamor_render.c      | 6 ++++++
 src/glamor_trapezoid.c   | 6 ++++++
 5 files changed, 23 insertions(+)

diff --git a/src/glamor_fill.c b/src/glamor_fill.c
index 2f08d72..fbc8739 100644
--- a/src/glamor_fill.c
+++ b/src/glamor_fill.c
@@ -244,10 +244,19 @@ _glamor_solid_boxes(PixmapPtr pixmap, BoxPtr box, int nbox, float *color)
 		if (box_cnt == 1)
 			dispatch->glDrawArrays(GL_TRIANGLE_FAN, 0, box_cnt * 4);
 		else
+#ifndef GLAMOR_GLES2
+			dispatch->glDrawRangeElements(GL_TRIANGLES,
+						      0,
+						      box_cnt * 4,
+						      box_cnt * 6,
+						      GL_UNSIGNED_SHORT,
+						      NULL);
+#else
 			dispatch->glDrawElements(GL_TRIANGLES,
 						 box_cnt * 6,
 						 GL_UNSIGNED_SHORT,
 						 NULL);
+#endif
 		nbox -= box_cnt;
 		box += box_cnt;
 	}
diff --git a/src/glamor_gl_dispatch.c b/src/glamor_gl_dispatch.c
index f996504..da99e26 100644
--- a/src/glamor_gl_dispatch.c
+++ b/src/glamor_gl_dispatch.c
@@ -54,6 +54,7 @@ glamor_gl_dispatch_init_impl(struct glamor_gl_dispatch *dispatch,
 	INIT_FUNC(dispatch, glMapBufferRange, get_proc_address);
 	INIT_FUNC(dispatch, glUnmapBuffer, get_proc_address);
 	INIT_FUNC(dispatch, glBlitFramebuffer, get_proc_address);
+	INIT_FUNC(dispatch, glDrawRangeElements, get_proc_address);
 #endif
 	INIT_FUNC(dispatch, glViewport, get_proc_address);
 	INIT_FUNC(dispatch, glDrawArrays, get_proc_address);
diff --git a/src/glamor_gl_dispatch.h b/src/glamor_gl_dispatch.h
index b3fc3a6..76dadd4 100644
--- a/src/glamor_gl_dispatch.h
+++ b/src/glamor_gl_dispatch.h
@@ -12,6 +12,7 @@ typedef struct glamor_gl_dispatch {
 
 	/* Elements Array*/
 	void (*glDrawElements) (GLenum mode, GLsizei count, GLenum type, const GLvoid * indices);
+	void (*glDrawRangeElements) (GLenum mode, GLuint start, GLuint end, GLsizei count, GLenum type, const GLvoid * indices);
 
 	/* Raster functions */
 	void (*glReadPixels) (GLint x, GLint y,
diff --git a/src/glamor_render.c b/src/glamor_render.c
index 27d5dc5..d2ac381 100644
--- a/src/glamor_render.c
+++ b/src/glamor_render.c
@@ -841,8 +841,14 @@ glamor_flush_composite_rects(ScreenPtr screen)
 	if (!glamor_priv->render_nr_verts)
 		return;
 
+#ifndef GLAMOR_GLES2
+	dispatch->glDrawRangeElements(GL_TRIANGLES, 0, glamor_priv->render_nr_verts,
+				      (glamor_priv->render_nr_verts * 3) / 2,
+				      GL_UNSIGNED_SHORT, NULL);
+#else
 	dispatch->glDrawElements(GL_TRIANGLES, (glamor_priv->render_nr_verts * 3) / 2,
 				 GL_UNSIGNED_SHORT, NULL);
+#endif
 	glamor_put_dispatch(glamor_priv);
 }
 
diff --git a/src/glamor_trapezoid.c b/src/glamor_trapezoid.c
index 7c934e3..76b3729 100644
--- a/src/glamor_trapezoid.c
+++ b/src/glamor_trapezoid.c
@@ -1543,8 +1543,14 @@ _glamor_generate_trapezoid_with_shader(ScreenPtr screen, PicturePtr picture,
 			        glamor_priv->vb, GL_DYNAMIC_DRAW);
 		}
 
+#ifndef GLAMOR_GLES2
+		dispatch->glDrawRangeElements(GL_TRIANGLES, 0, glamor_priv->render_nr_verts,
+			(glamor_priv->render_nr_verts * 3) / 2,
+		        GL_UNSIGNED_SHORT, NULL);
+#else
 		dispatch->glDrawElements(GL_TRIANGLES, (glamor_priv->render_nr_verts * 3) / 2,
 		        GL_UNSIGNED_SHORT, NULL);
+#endif
 	}
 
 	dispatch->glBindBuffer(GL_ARRAY_BUFFER, 0);
-- 
1.8.1.2