Bug fix: Fix --resize-damage

- Fix --resize-damage. I forgot to shrink the painting region back when
  actually copying to destination.

- Include extra pixels around the blur texture to avoid some possible
  small issues, if --resize-damage is positive.

- Known issue: Line artifacts may still appear with --dbe (X Render
  backend) or --glx-swap-method (GLX backend). I doubt if there's way to
  fix this without very inefficient mechanisms.

common.h

@@ -1599,6 +1599,9 @@ find_focused(session_t *ps) {
  */
 static inline XserverRegion
 copy_region(const session_t *ps, XserverRegion oldregion) {
+  if (!oldregion)
+    return None;
+
   XserverRegion region = XFixesCreateRegion(ps->dpy, NULL, 0);
 
   XFixesCopyRegion(ps->dpy, region, oldregion);

compton.c

@@ -1597,7 +1597,10 @@ rebuild_screen_reg(session_t *ps) {
 }
 
 static void
-paint_all(session_t *ps, XserverRegion region, win *t) {
+paint_all(session_t *ps, XserverRegion region, XserverRegion region_real, win *t) {
+  if (!region_real)
+    region_real = region;
+
 #ifdef DEBUG_REPAINT
   static struct timespec last_paint = { 0 };
 #endif
@@ -1645,7 +1648,8 @@ paint_all(session_t *ps, XserverRegion region, win *t) {
   }
 #endif
 
-  XFixesSetPictureClipRegion(ps->dpy, ps->tgt_picture, 0, 0, region);
+  if (BKEND_XRENDER == ps->o.backend)
+    XFixesSetPictureClipRegion(ps->dpy, ps->tgt_picture, 0, 0, region_real);
 
 #ifdef MONITOR_REPAINT
   switch (ps->o.backend) {
@@ -1820,7 +1824,7 @@ paint_all(session_t *ps, XserverRegion region, win *t) {
 #ifdef CONFIG_VSYNC_OPENGL
     case BKEND_GLX:
       if (ps->o.glx_use_copysubbuffermesa)
-        glx_swap_copysubbuffermesa(ps, region);
+        glx_swap_copysubbuffermesa(ps, region_real);
       else
         glXSwapBuffers(ps->dpy, get_tgt_window(ps));
       break;
@@ -6551,7 +6555,7 @@ session_run(session_t *ps) {
   t = paint_preprocess(ps, ps->list);
 
   if (ps->redirected)
-    paint_all(ps, None, t);
+    paint_all(ps, None, None, t);
 
   // Initialize idling
   ps->idling = false;
@@ -6587,10 +6591,13 @@ session_run(session_t *ps) {
     if (!ps->redirected)
       free_region(ps, &ps->all_damage);
 
+    XserverRegion all_damage_orig = None;
+    if (ps->o.resize_damage > 0)
+      all_damage_orig = copy_region(ps, ps->all_damage);
     resize_region(ps, ps->all_damage, ps->o.resize_damage);
     if (ps->all_damage && !is_region_empty(ps, ps->all_damage, NULL)) {
       static int paint = 0;
-      paint_all(ps, ps->all_damage, t);
+      paint_all(ps, ps->all_damage, all_damage_orig, t);
       ps->reg_ignore_expire = false;
       paint++;
       if (ps->o.benchmark && paint >= ps->o.benchmark)
@@ -6598,6 +6605,7 @@ session_run(session_t *ps) {
       XSync(ps->dpy, False);
       ps->all_damage = None;
     }
+    free_region(ps, &all_damage_orig);
 
     if (ps->idling)
       ps->fade_time = 0L;

compton.h

@@ -571,7 +571,7 @@ set_tgt_clip(session_t *ps, XserverRegion reg, const reg_data_t *pcache_reg) {
 }
 
 static void
-paint_all(session_t *ps, XserverRegion region, win *t);
+paint_all(session_t *ps, XserverRegion region, XserverRegion region_real, win *t);
 
 static void
 add_damage(session_t *ps, XserverRegion damage);

opengl.c

@@ -797,6 +797,18 @@ glx_blur_dst(session_t *ps, int dx, int dy, int width, int height, float z,
     return false;
   }
 
+  int mdx = dx, mdy = dy, mwidth = width, mheight = height;
+  if (ps->o.resize_damage > 0) {
+    int inc_x = min_i(ps->o.resize_damage, XFixedToDouble(ps->o.blur_kern[0]) / 2),
+        inc_y = min_i(ps->o.resize_damage, XFixedToDouble(ps->o.blur_kern[1]) / 2);
+    mdx = max_i(dx - inc_x, 0);
+    mdy = max_i(dy - inc_y, 0);
+    int mdx2 = min_i(dx + width + inc_x, ps->root_width),
+        mdy2 = min_i(dy + height + inc_y, ps->root_height);
+    mwidth = mdx2 - mdx;
+    mheight = mdy2 - mdy;
+  }
+
   GLenum tex_tgt = GL_TEXTURE_RECTANGLE;
   if (ps->glx_has_texture_non_power_of_two)
     tex_tgt = GL_TEXTURE_2D;
@@ -807,11 +819,11 @@ glx_blur_dst(session_t *ps, int dx, int dy, int width, int height, float z,
   glTexParameteri(tex_tgt, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
   glTexParameteri(tex_tgt, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
   glTexParameteri(tex_tgt, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
-  glTexImage2D(tex_tgt, 0, GL_RGB, width, height, 0, GL_BGRA, GL_UNSIGNED_BYTE, NULL);
-  glCopyTexSubImage2D(tex_tgt, 0, 0, 0, dx, ps->root_height - dy - height, width, height);
+  glTexImage2D(tex_tgt, 0, GL_RGB, mwidth, mheight, 0, GL_BGRA, GL_UNSIGNED_BYTE, NULL);
+  glCopyTexSubImage2D(tex_tgt, 0, 0, 0, mdx, ps->root_height - mdy - mheight, mwidth, mheight);
 
 #ifdef DEBUG_GLX
-  printf_dbgf("(): %d, %d, %d, %d\n", dx, ps->root_height - dy - height, width, height);
+  printf_dbgf("(): %d, %d, %d, %d\n", mdx, ps->root_height - mdy - mheight, mwidth, mheight);
 #endif
 
   // Paint it back
@@ -824,9 +836,9 @@ glx_blur_dst(session_t *ps, int dx, int dy, int width, int height, float z,
 #ifdef CONFIG_VSYNC_OPENGL_GLSL
   glUseProgram(ps->glx_prog_blur);
   if (ps->glx_prog_blur_unifm_offset_x >= 0)
-    glUniform1f(ps->glx_prog_blur_unifm_offset_x, 1.0f / width);
+    glUniform1f(ps->glx_prog_blur_unifm_offset_x, 1.0f / mwidth);
   if (ps->glx_prog_blur_unifm_offset_y >= 0)
-    glUniform1f(ps->glx_prog_blur_unifm_offset_y, 1.0f / height);
+    glUniform1f(ps->glx_prog_blur_unifm_offset_y, 1.0f / mheight);
   if (ps->glx_prog_blur_unifm_factor_center >= 0)
     glUniform1f(ps->glx_prog_blur_unifm_factor_center, factor_center);
 #endif
@@ -834,10 +846,10 @@ glx_blur_dst(session_t *ps, int dx, int dy, int width, int height, float z,
   {
     P_PAINTREG_START();
     {
-      const GLfloat rx = (double) (crect.x - dx) / width;
-      const GLfloat ry = 1.0 - (double) (crect.y - dy) / height;
-      const GLfloat rxe = rx + (double) crect.width / width;
-      const GLfloat rye = ry - (double) crect.height / height;
+      const GLfloat rx = (double) (crect.x - mdx) / mwidth;
+      const GLfloat ry = 1.0 - (double) (crect.y - mdy) / mheight;
+      const GLfloat rxe = rx + (double) crect.width / mwidth;
+      const GLfloat rye = ry - (double) crect.height / mheight;
       const GLfloat rdx = crect.x;
       const GLfloat rdy = ps->root_height - crect.y;
       const GLfloat rdxe = rdx + crect.width;