Feature: OpenGL backend

- Add experimental OpenGL backend (--opengl). --blur-background is
  currently not possible with this backend, because I'm still trying to
  find a proper way to do blur with OpenGL. Flipping backend on-the-fly
  is really hard, so it isn't supported right now. No configuration file
  option exists to enable this, because it isn't stable enough.

- Add `opengl-swc` VSync method that uses SGI_swap_control to control
  buffer swap, with OpenGL backend. (#7)

- Fix a potential read-from-freed-memory issue in paint_all().

- Correctly reattach GLX context after fork.

- Dump error text in error(). Add GLX error code handling.

- Code clean-up.

- Known issues: Region operations take a lot of time in glx_render().
  I'm hesitating about what to do.

1 files changed, 84 insertions, 53 deletions

diff --git a/compton.h b/compton.h
index f0af56482..0479b3d0a 100644
--- a/compton.h
+++ b/compton.h
@@ -9,7 +9,6 @@
 
 #include "common.h"
 
-#include <ctype.h>
 #include <math.h>
 #include <sys/select.h>
 #include <limits.h>
@@ -53,14 +52,6 @@ static int
 should_ignore(session_t *ps, unsigned long sequence);
 
 /**
- * Return the painting target window.
- */
-static inline Window
-get_tgt_window(session_t *ps) {
-  return ps->o.paint_on_overlay ? ps->overlay: ps->root;
-}
-
-/**
  * Reset filter on a <code>Picture</code>.
  */
 static inline void
@@ -119,16 +110,6 @@ array_wid_exists(const Window *arr, int count, Window wid) {
 
   return false;
 }
-/**
- * Destroy a <code>XserverRegion</code>.
- */
-inline static void
-free_region(session_t *ps, XserverRegion *p) {
-  if (*p) {
-    XFixesDestroyRegion(ps->dpy, *p);
-    *p = None;
-  }
-}
 
 /**
  * Destroy a <code>Picture</code>.
@@ -177,15 +158,57 @@ free_wincondlst(c2_lptr_t **pcondlst) {
 #endif
 
 /**
+ * Check whether a paint_t contains enough data.
+ */
+static inline bool
+paint_isvalid(session_t *ps, const paint_t *ppaint) {
+  if (!ppaint || !ppaint->pixmap)
+    return false;
+
+  if (BKEND_XRENDER == ps->o.backend && !ppaint->pict)
+    return false;
+
+#ifdef CONFIG_VSYNC_OPENGL
+  if (BKEND_GLX == ps->o.backend && !glx_tex_binded(ppaint->ptex))
+    return false;
+#endif
+
+  return true;
+}
+/**
+ * Bind texture in paint_t if we are using OpenGL backend.
+ */
+static inline bool
+paint_bind_tex(session_t *ps, paint_t *ppaint, int wid, int hei, int depth) {
+#ifdef CONFIG_VSYNC_OPENGL
+  // TODO: Make sure we have the same Pixmap binded?
+  if (BKEND_GLX == ps->o.backend && !glx_tex_binded(ppaint->ptex)) {
+    return glx_bind_pixmap(ps, &ppaint->ptex, ppaint->pixmap, wid, hei, depth);
+  }
+#endif
+
+  return true;
+}
+
+/**
+ * Free paint_t.
+ */
+static inline void
+free_paint(session_t *ps, paint_t *ppaint) {
+  free_texture(ps, &ppaint->ptex);
+  free_picture(ps, &ppaint->pict);
+  free_pixmap(ps, &ppaint->pixmap);
+}
+
+/**
  * Destroy all resources in a <code>struct _win</code>.
  */
-inline static void
+static inline void
 free_win_res(session_t *ps, win *w) {
   free_region(ps, &w->extents);
-  free_pixmap(ps, &w->pixmap);
-  free_picture(ps, &w->picture);
+  free_paint(ps, &w->paint);
   free_region(ps, &w->border_size);
-  free_picture(ps, &w->shadow_pict);
+  free_paint(ps, &w->shadow_paint);
   free_damage(ps, &w->damage);
   free_region(ps, &w->reg_ignore);
   free(w->name);
@@ -195,6 +218,19 @@ free_win_res(session_t *ps, win *w) {
 }
 
 /**
+ * Free root tile related things.
+ */
+static inline void
+free_root_tile(session_t *ps) {
+  free_picture(ps, &ps->root_tile_paint.pict);
+  free_texture(ps, &ps->root_tile_paint.ptex);
+  if (ps->root_tile_fill)
+    free_pixmap(ps, &ps->root_tile_paint.pixmap);
+  ps->root_tile_paint.pixmap = None;
+  ps->root_tile_fill = false;
+}
+
+/**
  * Get current system clock in milliseconds.
  */
 static inline time_ms_t
@@ -274,8 +310,8 @@ presum_gaussian(session_t *ps, conv *map);
 static XImage *
 make_shadow(session_t *ps, double opacity, int width, int height);
 
-static Picture
-shadow_picture(session_t *ps, double opacity, int width, int height);
+static bool
+win_build_shadow(session_t *ps, win *w, double opacity);
 
 static Picture
 solid_picture(session_t *ps, bool argb, double a,
@@ -463,11 +499,11 @@ group_is_focused(session_t *ps, Window leader) {
 static win *
 recheck_focus(session_t *ps);
 
-static Picture
-root_tile_f(session_t *ps);
+static bool
+get_root_tile(session_t *ps);
 
 static void
-paint_root(session_t *ps, Picture tgt_buffer);
+paint_root(session_t *ps, XserverRegion reg_paint);
 
 static XserverRegion
 win_get_region(session_t *ps, win *w, bool use_offset);
@@ -491,6 +527,22 @@ static win *
 paint_preprocess(session_t *ps, win *list);
 
 static void
+render(session_t *ps, int x, int y, int dx, int dy, int wid, int hei,
+    double opacity, bool argb, bool neg,
+    Picture pict, glx_texture_t *ptex, XserverRegion reg_paint);
+
+static inline void
+win_render(session_t *ps, win *w, int x, int y, int wid, int hei, double opacity, XserverRegion reg_paint, Picture pict) {
+  const int dx = (w ? w->a.x: 0) + x;
+  const int dy = (w ? w->a.y: 0) + y;
+  const bool argb = (w && w->mode == WMODE_ARGB);
+  const bool neg = (w && w->invert_color);
+
+  render(ps, x, y, dx, dy, wid, hei, opacity, argb, neg,
+      pict, (w ? w->paint.ptex: ps->root_tile_paint.ptex), reg_paint);
+}
+
+static void
 paint_all(session_t *ps, XserverRegion region, win *t);
 
 static void
@@ -887,39 +939,15 @@ swopti_init(session_t *ps);
 static void
 swopti_handle_timeout(session_t *ps, struct timeval *ptv);
 
-static bool
-opengl_init(session_t *ps, bool need_render);
-
-static void
-opengl_destroy(session_t *ps);
-
 #ifdef CONFIG_VSYNC_OPENGL
 /**
- * Check if a GLX extension exists.
- */
-static inline bool
-opengl_hasext(session_t *ps, const char *ext) {
-  const char *glx_exts = glXQueryExtensionsString(ps->dpy, ps->scr);
-  const char *pos = strstr(glx_exts, ext);
-  // Make sure the extension string is matched as a whole word
-  if (!pos
-      || ((pos - glx_exts) && !isspace(*(pos - 1)))
-      || (strlen(pos) > strlen(ext) && !isspace(pos[strlen(ext)]))) {
-    printf_errf("(): Missing OpenGL extension %s.", ext);
-    return false;
-  }
-
-  return true;
-}
-
-/**
  * Ensure we have a GLX context.
  */
 static inline bool
 ensure_glx_context(session_t *ps) {
   // Create GLX context
   if (!ps->glx_context)
-    opengl_init(ps, false);
+    glx_init(ps, false);
 
   return ps->glx_context;
 }
@@ -939,6 +967,9 @@ vsync_opengl_init(session_t *ps);
 static bool
 vsync_opengl_oml_init(session_t *ps);
 
+static bool
+vsync_opengl_swc_init(session_t *ps);
+
 #ifdef CONFIG_VSYNC_OPENGL
 static int
 vsync_opengl_wait(session_t *ps);