From d5ba32711fdc4c589bf5755efac7d10218bf5217 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sun, 13 Dec 2015 21:02:31 +0200
Subject: [PATCH] Render root pixmap if available

---
 source/main.c | 76 +++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 65 insertions(+), 11 deletions(-)

diff --git a/source/main.c b/source/main.c
index 185c6b4..a1bfe6a 100644
--- a/source/main.c
+++ b/source/main.c
@@ -71,6 +71,9 @@ typedef struct CompositedScreen
 	unsigned window_vertex_array;
 	unsigned framebuffer;
 	unsigned fb_texture;
+	Pixmap root_pixmap;
+	GLXPixmap root_glx_pixmap;
+	unsigned root_texture;
 	CompositedWindow *windows;
 	unsigned nwindows;
 	unsigned windows_capacity;
@@ -89,6 +92,7 @@ typedef struct Compositor
 	PFNGLXCREATECONTEXTATTRIBSARBPROC glXCreateContextAttribsARB;
 	PFNGLXBINDTEXIMAGEEXTPROC glXBindTexImageEXT;
 	PFNGLXRELEASETEXIMAGEEXTPROC glXReleaseTexImageEXT;
+	Atom root_pmap_atom;
 	Atom correction_atom;
 	Atom monitors_atom;
 	int dirty;
@@ -325,6 +329,8 @@ int create_gl_resources(CompositedScreen *screen)
 	glDepthMask(GL_FALSE);
 	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
 
+	screen->root_texture = create_2d_texture();
+
 	return 1;
 }
 
@@ -357,17 +363,11 @@ CompositedWindow *find_window_global(Compositor *compositor, Window w, Composite
 	return NULL;
 }
 
-void create_window_pixmap(Compositor *compositor, CompositedScreen *screen, CompositedWindow *window)
+GLXPixmap pixmap_to_glx_pixmap(Compositor *compositor, CompositedScreen *screen, Pixmap pixmap)
 {
 	int attribs[5];
 	unsigned i;
 
-	if(window->pixmap)
-	{
-		glXDestroyPixmap(compositor->display, window->glx_pixmap);
-		XFreePixmap(compositor->display, window->pixmap);
-	}
-
 	i = 0;
 	attribs[i++] = GLX_TEXTURE_TARGET_EXT;
 	attribs[i++] = GLX_TEXTURE_2D_EXT;
@@ -375,8 +375,19 @@ void create_window_pixmap(Compositor *compositor, CompositedScreen *screen, Comp
 	attribs[i++] = GLX_TEXTURE_FORMAT_RGBA_EXT;
 	attribs[i++] = None;
 
+	return glXCreatePixmap(compositor->display, screen->fbconfig, pixmap, attribs);
+}
+
+void create_window_pixmap(Compositor *compositor, CompositedScreen *screen, CompositedWindow *window)
+{
+	if(window->pixmap)
+	{
+		glXDestroyPixmap(compositor->display, window->glx_pixmap);
+		XFreePixmap(compositor->display, window->pixmap);
+	}
+
 	window->pixmap = XCompositeNameWindowPixmap(compositor->display, window->window);
-	window->glx_pixmap = glXCreatePixmap(compositor->display, screen->fbconfig, window->pixmap, attribs);
+	window->glx_pixmap = pixmap_to_glx_pixmap(compositor, screen, window->pixmap);
 	window->recreate_pixmap = 0;
 }
 
@@ -796,6 +807,33 @@ void update_geometry_correction(Compositor *compositor, CompositedScreen *screen
 	XFree(values);
 }
 
+void update_root_pixmap(Compositor *compositor, CompositedScreen *screen)
+{
+	Atom prop_type;
+	int prop_format;
+	unsigned long overflow;
+	unsigned long length;
+	long *pixmap;
+
+	XGetWindowProperty(compositor->display, screen->root, compositor->root_pmap_atom, 0, 1, False, XA_PIXMAP,
+		&prop_type, &prop_format, &length, &overflow, (unsigned char **)&pixmap);
+	if(prop_type!=XA_PIXMAP || prop_format!=32)
+	{
+		screen->root_pixmap = 0;
+		if(screen->root_glx_pixmap)
+		{
+			glXDestroyPixmap(compositor->display, screen->root_glx_pixmap);
+			screen->root_glx_pixmap = 0;
+		}
+		return;
+	}
+
+	screen->root_pixmap = pixmap[0];
+	screen->root_glx_pixmap = pixmap_to_glx_pixmap(compositor, screen, screen->root_pixmap);
+
+	XFree(pixmap);
+}
+
 int initialize_screen(Compositor *compositor, unsigned number)
 {
 	CompositedScreen *screen;
@@ -842,6 +880,7 @@ int initialize_screen(Compositor *compositor, unsigned number)
 	XRRFreeScreenResources(xrr_res);
 
 	update_geometry_correction(compositor, screen);
+	update_root_pixmap(compositor, screen);
 
 	XQueryTree(compositor->display, screen->root, &dummy_root, &dummy_parent, &children, &nchildren);
 
@@ -912,6 +951,7 @@ int initialize_compositor(Compositor *compositor)
 	compositor->glXBindTexImageEXT = (PFNGLXBINDTEXIMAGEEXTPROC)glXGetProcAddress((unsigned char *)"glXBindTexImageEXT");
 	compositor->glXReleaseTexImageEXT = (PFNGLXRELEASETEXIMAGEEXTPROC)glXGetProcAddress((unsigned char *)"glXReleaseTexImageEXT");
 
+	compositor->root_pmap_atom = XInternAtom(compositor->display, "_XROOTPMAP_ID", False);
 	compositor->correction_atom = XInternAtom(compositor->display, "GEOMETRY_CORRECTION", False);
 	compositor->monitors_atom = XInternAtom(compositor->display, "GEOMETRY_CORRECTION_MONITORS", False);
 
@@ -1204,11 +1244,25 @@ void refresh_screen(Compositor *compositor, CompositedScreen *screen)
 
 	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, screen->framebuffer);
 
-	glClearColor(0.5f, 0.5f, 0.5f, 0.0f);
-	glClear(GL_COLOR_BUFFER_BIT);
-
 	use_mask = -1;
 	glBindVertexArray(screen->window_vertex_array);
+
+	if(screen->root_pixmap)
+	{
+		use_mask = 0;
+		glUseProgram(screen->program);
+		glBindTexture(GL_TEXTURE_2D, screen->root_texture);
+		compositor->glXBindTexImageEXT(compositor->display, screen->root_glx_pixmap, GLX_FRONT_LEFT_EXT, NULL);
+		glUniform4f(screen->geometry_loc, 0.0f, 0.0f, 1.0f, 1.0f);
+		glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+		compositor->glXReleaseTexImageEXT(compositor->display, screen->root_glx_pixmap, GLX_FRONT_LEFT_EXT);
+	}
+	else
+	{
+		glClearColor(0.5f, 0.5f, 0.5f, 0.0f);
+		glClear(GL_COLOR_BUFFER_BIT);
+	}
+
 	for(i=0; i<screen->nwindows; ++i)
 	{
 		CompositedWindow *window;
-- 
2.45.2