Bug fix: GLX: ARGB texture too dark & Jitter when resize & others

- GLX backend: Fix a bug that ARGB windows / shadows are rendered too
  dark. Thanks to derhass in FreeNode/##opengl for help.

- GLX backend: Fix a problem that during window resize the content looks
  jittering, by letting compton fetch pixmap sizes with XGetGeometry()
  instead of relying on window width/height, which could be inaccurate
  during window resize. Negative effect on performance. Thanks to M4he
  for reporting. (#7)

- Add .desktop file. Thanks to quequotion for providing it. (#97)

- Avoid checking presence of window pixmap, because they may not exist
  with very old X Composite implementations.

- Add workaround for a strange window restack issue when compton
  receieves a ConfigureNotify with non-existent new above window.

- Add debugging function hexdump(). Extra sanity checks on various
  places.

4 files changed, 117 insertions, 42 deletions

diff --git a/common.h b/common.h
index 77aa582f6..3b6620854 100644
--- a/common.h
+++ b/common.h
@@ -297,9 +297,9 @@ struct _glx_texture {
   GLuint texture;
   GLXPixmap glpixmap;
   Pixmap pixmap;
-  int width;
-  int height;
-  int depth;
+  unsigned width;
+  unsigned height;
+  unsigned depth;
   bool y_inverted;
 };
 #endif
@@ -1573,7 +1573,7 @@ glx_init_blur(session_t *ps);
 
 bool
 glx_bind_pixmap(session_t *ps, glx_texture_t **pptex, Pixmap pixmap,
-    int width, int height, int depth);
+    unsigned width, unsigned height, unsigned depth);
 
 void
 glx_release_pixmap(session_t *ps, glx_texture_t *ptex);
@@ -1686,3 +1686,39 @@ c2_match(session_t *ps, win *w, const c2_lptr_t *condlst,
 ///@}
 
 #endif
+
+/**
+ * @brief Dump raw bytes in HEX format.
+ *
+ * @param data pointer to raw data
+ * @param len length of data
+ */
+static inline void
+hexdump(const char *data, int len) {
+  static const int BYTE_PER_LN = 16;
+
+  if (len <= 0)
+    return;
+
+  // Print header
+  printf("%10s:", "Offset");
+  for (int i = 0; i < BYTE_PER_LN; ++i)
+    printf(" %2d", i);
+  putchar('\n');
+
+  // Dump content
+  for (int offset = 0; offset < len; ++offset) {
+    if (!(offset % BYTE_PER_LN))
+      printf("0x%08x:", offset);
+
+    printf(" %02hhx", data[offset]);
+
+    if ((BYTE_PER_LN - 1) == offset % BYTE_PER_LN)
+      putchar('\n');
+  }
+  if (len % BYTE_PER_LN)
+    putchar('\n');
+
+  fflush(stdout);
+}
+
diff --git a/compton.c b/compton.c
index 591fc7043..539f8d201 100644
--- a/compton.c
+++ b/compton.c
@@ -474,6 +474,7 @@ win_build_shadow(session_t *ps, win *w, double opacity) {
 
   w->shadow_paint.pixmap = shadow_pixmap_argb;
   w->shadow_paint.pict = shadow_picture_argb;
+
   bool success = paint_bind_tex(ps, &w->shadow_paint, shadow_image->width, shadow_image->height, 32, true);
 
   XFreeGC(ps->dpy, gc);
@@ -863,8 +864,7 @@ get_root_tile(session_t *ps) {
   ps->root_tile_paint.pixmap = pixmap;
 #ifdef CONFIG_VSYNC_OPENGL
   if (BKEND_GLX == ps->o.backend)
-    return glx_bind_pixmap(ps, &ps->root_tile_paint.ptex, ps->root_tile_paint.pixmap,
-        ps->root_width, ps->root_height, ps->depth);
+    return glx_bind_pixmap(ps, &ps->root_tile_paint.ptex, ps->root_tile_paint.pixmap, 0, 0, 0);
 #endif
 
   return true;
@@ -1437,8 +1437,10 @@ win_paint_win(session_t *ps, win *w, XserverRegion reg_paint) {
     }
   }
   // GLX: Build texture
-  if (!paint_bind_tex(ps, &w->paint, w->widthb, w->heightb,
-        w->pictfmt->depth, w->pixmap_damaged)) {
+  // Let glx_bind_pixmap() determine pixmap size, because if the user
+  // is resizing windows, the width and height we get may not be up-to-date,
+  // causing the jittering issue M4he reported in #7.
+  if (!paint_bind_tex(ps, &w->paint, 0, 0, 0, w->pixmap_damaged)) {
     printf_errf("(%#010lx): Failed to bind texture. Expect troubles.", w->id);
   }
   w->pixmap_damaged = false;
@@ -2633,21 +2635,33 @@ restack_win(session_t *ps, win *w, Window new_above) {
   }
 
   if (old_above != new_above) {
-    win **prev;
+    win **prev = NULL, **prev_old = NULL;
 
-    /* unhook */
+    // unhook
     for (prev = &ps->list; *prev; prev = &(*prev)->next) {
       if ((*prev) == w) break;
     }
 
-    *prev = w->next;
+    prev_old = prev;
+
+    bool found = false;
 
-    /* rehook */
+    // rehook
     for (prev = &ps->list; *prev; prev = &(*prev)->next) {
-      if ((*prev)->id == new_above && !(*prev)->destroyed)
+      if ((*prev)->id == new_above && !(*prev)->destroyed) {
+        found = true;
         break;
+      }
     }
 
+    if (!found) {
+      printf_errf("(%#010lx, %#010lx): "
+          "Failed to found new above window.", w->id, new_above);
+      return;
+    }
+
+    *prev_old = w->next;
+
     w->next = *prev;
     *prev = w;
 
@@ -2668,7 +2682,9 @@ restack_win(session_t *ps, win *w, Window new_above) {
 
         desc = "";
         if (c->destroyed) desc = "(D) ";
-        printf("%#010lx \"%s\" %s-> ", c->id, window_name, desc);
+        printf("%#010lx \"%s\" %s", c->id, window_name, desc);
+        if (c->next)
+          printf("-> ");
 
         if (to_free) {
           XFree(window_name);
diff --git a/compton.h b/compton.h
index 9c4bd0a9f..c16c59612 100644
--- a/compton.h
+++ b/compton.h
@@ -162,7 +162,9 @@ free_wincondlst(c2_lptr_t **pcondlst) {
  */
 static inline bool
 paint_isvalid(session_t *ps, const paint_t *ppaint) {
-  if (!ppaint || !ppaint->pixmap)
+  // Don't check for presence of Pixmap here, because older X Composite doesn't
+  // provide it
+  if (!ppaint)
     return false;
 
   if (BKEND_XRENDER == ps->o.backend && !ppaint->pict)
@@ -179,13 +181,15 @@ paint_isvalid(session_t *ps, const paint_t *ppaint) {
  * Bind texture in paint_t if we are using GLX backend.
  */
 static inline bool
-paint_bind_tex(session_t *ps, paint_t *ppaint, int wid, int hei, int depth,
-    bool force) {
+paint_bind_tex(session_t *ps, paint_t *ppaint,
+    unsigned wid, unsigned hei, unsigned depth, bool force) {
 #ifdef CONFIG_VSYNC_OPENGL
-  // TODO: Make sure we have the same Pixmap binded?
-  if (BKEND_GLX == ps->o.backend
-      && (force || !glx_tex_binded(ppaint->ptex, ppaint->pixmap))) {
-    return glx_bind_pixmap(ps, &ppaint->ptex, ppaint->pixmap, wid, hei, depth);
+  if (BKEND_GLX == ps->o.backend) {
+    if (!ppaint->pixmap)
+      return false;
+
+    if (force || !glx_tex_binded(ppaint->ptex, ppaint->pixmap))
+      return glx_bind_pixmap(ps, &ppaint->ptex, ppaint->pixmap, wid, hei, depth);
   }
 #endif
 
diff --git a/opengl.c b/opengl.c
index b32368e2f..21b3c181f 100644
--- a/opengl.c
+++ b/opengl.c
@@ -107,7 +107,6 @@ glx_init(session_t *ps, bool need_render) {
 
     // glEnable(GL_DEPTH_TEST);
     glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
-    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
     glDisable(GL_BLEND);
 
     if (!ps->o.glx_no_stencil) {
@@ -322,15 +321,10 @@ glx_cmp_fbconfig(session_t *ps,
  */
 bool
 glx_bind_pixmap(session_t *ps, glx_texture_t **pptex, Pixmap pixmap,
-    int width, int height, int depth) {
-  if (depth > OPENGL_MAX_DEPTH) {
-    printf_errf("(%d): Requested depth higher than %d.", depth,
-        OPENGL_MAX_DEPTH);
-    return false;
-  }
-  const glx_fbconfig_t *pcfg = ps->glx_fbconfigs[depth];
-  if (!pcfg) {
-    printf_errf("(%d): Couldn't find FBConfig with requested depth.", depth);
+    unsigned width, unsigned height, unsigned depth) {
+  if (!pixmap) {
+    printf_errf("(%#010lx): Binding to an empty pixmap. This can't work.",
+        pixmap);
     return false;
   }
 
@@ -359,8 +353,7 @@ glx_bind_pixmap(session_t *ps, glx_texture_t **pptex, Pixmap pixmap,
   glEnable(target);
 
   // Release pixmap if parameters are inconsistent
-  if (ptex->texture && !(width == ptex->width && height == ptex->height
-        && ptex->pixmap == pixmap && depth == ptex->depth)) {
+  if (ptex->texture && ptex->pixmap != pixmap) {
     glx_release_pixmap(ps, ptex);
   }
 
@@ -380,7 +373,6 @@ glx_bind_pixmap(session_t *ps, glx_texture_t **pptex, Pixmap pixmap,
     glBindTexture(target, 0);
 
     ptex->texture = texture;
-    ptex->y_inverted = pcfg->y_inverted;
   }
   if (!ptex->texture) {
     printf_errf("(): Failed to allocate texture.");
@@ -393,6 +385,29 @@ glx_bind_pixmap(session_t *ps, glx_texture_t **pptex, Pixmap pixmap,
   if (!ptex->glpixmap) {
     need_release = false;
 
+    // Retrieve pixmap parameters, if they aren't provided
+    if (!(width && height && depth)) {
+      Window rroot = None;
+      int rx = 0, ry = 0;
+      unsigned rbdwid = 0;
+      if (!XGetGeometry(ps->dpy, pixmap, &rroot, &rx, &ry,
+            &width, &height, &rbdwid, &depth)) {
+        printf_errf("(%#010lx): Failed to query Pixmap info.", pixmap);
+        return false;
+      }
+      if (depth > OPENGL_MAX_DEPTH) {
+        printf_errf("(%d): Requested depth higher than %d.", depth,
+            OPENGL_MAX_DEPTH);
+        return false;
+      }
+    }
+
+    const glx_fbconfig_t *pcfg = ps->glx_fbconfigs[depth];
+    if (!pcfg) {
+      printf_errf("(%d): Couldn't find FBConfig with requested depth.", depth);
+      return false;
+    }
+
     // Determine texture target, copied from compiz
     GLint tex_tgt = 0;
     if (GLX_TEXTURE_2D_BIT_EXT & pcfg->texture_tgts
@@ -419,6 +434,11 @@ glx_bind_pixmap(session_t *ps, glx_texture_t **pptex, Pixmap pixmap,
     };
 
     ptex->glpixmap = glXCreatePixmap(ps->dpy, pcfg->cfg, pixmap, attrs);
+    ptex->pixmap = pixmap;
+    ptex->width = width;
+    ptex->height = height;
+    ptex->depth = depth;
+    ptex->y_inverted = pcfg->y_inverted;
   }
   if (!ptex->glpixmap) {
     printf_errf("(): Failed to allocate GLX pixmap.");
@@ -436,11 +456,6 @@ glx_bind_pixmap(session_t *ps, glx_texture_t **pptex, Pixmap pixmap,
   glBindTexture(target, 0);
   glDisable(target);
 
-  ptex->width = width;
-  ptex->height = height;
-  ptex->depth = depth;
-  ptex->pixmap = pixmap;
-
   return true;
 }
 
@@ -493,7 +508,7 @@ glx_set_clip(session_t *ps, XserverRegion reg) {
       GLint z = 0;
 
 #ifdef DEBUG_GLX
-      printf_dbgf("(): Rect %d: %f, %f, %f, %f\n", i, rx, ry, rxe, rye);
+      printf_dbgf("(): Rect %d: %d, %d, %d, %d\n", i, rx, ry, rxe, rye);
 #endif
 
       glVertex3i(rx, ry, z);
@@ -532,10 +547,14 @@ glx_render(session_t *ps, const glx_texture_t *ptex,
   if (opacity < 1.0 || GLX_TEXTURE_FORMAT_RGBA_EXT ==
       ps->glx_fbconfigs[ptex->depth]->texture_fmt) {
     glEnable(GL_BLEND);
-    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+
     // Needed for handling opacity of ARGB texture
     glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
-    glColor4f(1.0f, 1.0f, 1.0f, opacity);
+
+    // This is all weird, but X Render is using a strange ARGB format, and
+    // we need to use those things to correct it. Thanks to derhass for help.
+    glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
+    glColor4f(opacity, opacity, opacity, opacity);
   }
 
   // Color negation