Fix so many things that there is little place in this column to list them all...

Fix so many things that there is little place in this column to list them all but the result is that blending modes just work now for drawing primitives.

Fixes involved:
1. Fix handling of alpha channel when SDL_BLENDMODE_NONE is set.
2. Make xrendercolor use floating-point values for color channels and then convert to 16 bit ints.
3. Fix handling of visuals in SDL_x11modes.c so that a 32 bit ARGB visual is used.
4. Fix the background pixel value in SDL_x11window.c so that the window background has an alpha value of 0xFF and not 0.

src/video/x11/SDL_x11modes.c

@@ -23,7 +23,7 @@
 
 #include "SDL_x11video.h"
 
-//#define X11MODES_DEBUG
+#define X11MODES_DEBUG
 #undef SDL_VIDEO_DRIVER_X11_XINERAMA
 #undef SDL_VIDEO_DRIVER_X11_XRANDR
 #undef SDL_VIDEO_DRIVER_X11_VIDMODE
@@ -33,11 +33,12 @@ get_visualinfo(Display * display, int screen, XVisualInfo * vinfo)
 {
     const char *visual_id = SDL_getenv("SDL_VIDEO_X11_VISUALID");
     int depth;
+    XVisualInfo *vi;
+    int nvis;
 
     /* Look for an exact visual, if requested */
     if (visual_id) {
-        XVisualInfo *vi, template;
-        int nvis;
+        XVisualInfo template;
 
         SDL_zero(template);
         template.visualid = SDL_strtol(visual_id, NULL, 0);
@@ -48,7 +49,22 @@ get_visualinfo(Display * display, int screen, XVisualInfo * vinfo)
             return 0;
         }
     }
-
+#ifdef SDL_VIDEO_DRIVER_X11_XRENDER
+    depth = 32;
+    long vinfo_mask;
+    XVisualInfo vinfo_templ;
+    vinfo_mask = (VisualDepthMask | VisualRedMaskMask | VisualGreenMaskMask | VisualBlueMaskMask);
+    vinfo_templ.depth = 32;
+    vinfo_templ.red_mask = 0xFF0000;
+    vinfo_templ.green_mask = 0xFF00;
+    vinfo_templ.blue_mask = 0xFF;
+    vi = XGetVisualInfo(display, vinfo_mask, &vinfo_templ, &nvis);
+    if(vi) {
+        *vinfo = *vi;
+        XFree(vi);
+        return 0;
+    }
+#endif
     depth = DefaultDepth(display, screen);
     if ((X11_UseDirectColorVisuals() &&
          XMatchVisualInfo(display, screen, depth, DirectColor, vinfo)) ||

src/video/x11/SDL_x11render.c

@@ -215,11 +215,37 @@ X11_CreateRenderer(SDL_Window * window, Uint32 flags)
     data->depth = displaydata->depth;
     data->scanline_pad = displaydata->scanline_pad;
     data->xwindow = windowdata->xwindow;
+    
+    renderer->DisplayModeChanged = X11_DisplayModeChanged;
+    renderer->CreateTexture = X11_CreateTexture;
+    renderer->QueryTexturePixels = X11_QueryTexturePixels;
+    renderer->SetTextureBlendMode = X11_SetTextureBlendMode;
+    renderer->SetTextureScaleMode = X11_SetTextureScaleMode;
+    renderer->UpdateTexture = X11_UpdateTexture;
+    renderer->LockTexture = X11_LockTexture;
+    renderer->UnlockTexture = X11_UnlockTexture;
+    renderer->SetDrawBlendMode = X11_SetDrawBlendMode;
+    renderer->RenderDrawPoints = X11_RenderDrawPoints;
+    renderer->RenderDrawLines = X11_RenderDrawLines;
+    renderer->RenderDrawRects = X11_RenderDrawRects;
+    renderer->RenderFillRects = X11_RenderFillRects;
+    renderer->RenderCopy = X11_RenderCopy;
+    renderer->RenderReadPixels = X11_RenderReadPixels;
+    renderer->RenderWritePixels = X11_RenderWritePixels;
+    renderer->RenderPresent = X11_RenderPresent;
+    renderer->DestroyTexture = X11_DestroyTexture;
+    renderer->DestroyRenderer = X11_DestroyRenderer;
+    renderer->info = X11_RenderDriver.info;
+    renderer->window = window;
+    renderer->driverdata = data;
+
+    renderer->info.flags = SDL_RENDERER_ACCELERATED;
+
 #ifdef SDL_VIDEO_DRIVER_X11_XRENDER
     int event_basep, error_basep;
     if(XRenderQueryExtension(data->display, &event_basep, &error_basep) == True) {
         data->use_xrender = SDL_TRUE;
-        data->xwindow_pict_fmt = XRenderFindVisualFormat(data->display, data->visual);
+        data->xwindow_pict_fmt = XRenderFindStandardFormat(data->display, PictStandardARGB32);
         if(!data->xwindow_pict_fmt) {
             data->use_xrender = SDL_FALSE;
             goto fallback;
@@ -230,6 +256,8 @@ X11_CreateRenderer(SDL_Window * window, Uint32 flags)
             data->use_xrender = SDL_FALSE;
             goto fallback;
         }
+        renderer->info.blend_modes |=
+            (SDL_BLENDMODE_BLEND | SDL_BLENDMODE_ADD | SDL_BLENDMODE_MASK);
         // Create a 1 bit depth mask
         data->mask = XCreatePixmap(data->display, data->xwindow,
                                    window->w, window->h, 1);
@@ -241,37 +269,15 @@ X11_CreateRenderer(SDL_Window * window, Uint32 flags)
         gcv_mask.foreground = 1;
         gcv_mask.background = 0;
         data->mask_gc = XCreateGC(data->display, data->mask, GCBackground | GCForeground, &gcv_mask);
+        renderer->blendMode = SDL_BLENDMODE_BLEND;
+        data->blend_op = PictOpOver;
     }
     else {
         data->use_xrender = SDL_FALSE;
     }
     fallback:
 #endif
-    renderer->DisplayModeChanged = X11_DisplayModeChanged;
-    renderer->CreateTexture = X11_CreateTexture;
-    renderer->QueryTexturePixels = X11_QueryTexturePixels;
-    renderer->SetTextureBlendMode = X11_SetTextureBlendMode;
-    renderer->SetTextureScaleMode = X11_SetTextureScaleMode;
-    renderer->UpdateTexture = X11_UpdateTexture;
-    renderer->LockTexture = X11_LockTexture;
-    renderer->UnlockTexture = X11_UnlockTexture;
-    renderer->SetDrawBlendMode = X11_SetDrawBlendMode;
-    renderer->RenderDrawPoints = X11_RenderDrawPoints;
-    renderer->RenderDrawLines = X11_RenderDrawLines;
-    renderer->RenderDrawRects = X11_RenderDrawRects;
-    renderer->RenderFillRects = X11_RenderFillRects;
-    renderer->RenderCopy = X11_RenderCopy;
-    renderer->RenderReadPixels = X11_RenderReadPixels;
-    renderer->RenderWritePixels = X11_RenderWritePixels;
-    renderer->RenderPresent = X11_RenderPresent;
-    renderer->DestroyTexture = X11_DestroyTexture;
-    renderer->DestroyRenderer = X11_DestroyRenderer;
-    renderer->info = X11_RenderDriver.info;
-    renderer->window = window;
-    renderer->driverdata = data;
-
-    renderer->info.flags = SDL_RENDERER_ACCELERATED;
-
+    
     if (flags & SDL_RENDERER_SINGLEBUFFER) {
         renderer->info.flags |=
             (SDL_RENDERER_SINGLEBUFFER | SDL_RENDERER_PRESENTCOPY);
@@ -734,26 +740,30 @@ X11_SetDrawBlendMode(SDL_Renderer * renderer)
     switch (renderer->blendMode) {
     case SDL_BLENDMODE_NONE:
 #ifdef SDL_VIDEO_DRIVER_X11_XRENDER
+        //PictOpSrc
         data->blend_op = PictOpSrc;
         return 0;
-    case SDL_BLENDMODE_MASK: // Use src pict as mask
-        data->blend_op = PictOpSrc;
+    case SDL_BLENDMODE_BLEND: // PictOpOver
+        data->blend_op = PictOpOver;
         return 0;
     case SDL_BLENDMODE_ADD: // PictOpAdd
         data->blend_op = PictOpAdd;
         return 0;
-    case SDL_BLENDMODE_BLEND: // PictOpOver
-        data->blend_op = PictOpOver;
-        return 0;
     /* FIXME case SDL_BLENDMODE_MOD: */
 #endif
         return 0;
     default:
         SDL_Unsupported();
-        renderer->blendMode = SDL_BLENDMODE_NONE;
 #ifdef SDL_VIDEO_DRIVER_X11_XRENDER
-        data->blend_op = PictOpSrc;
+        if(data->use_xrender) {
+            renderer->blendMode = SDL_BLENDMODE_BLEND;
+            data->blend_op = PictOpOver;
+        }
+        else
 #endif
+        {
+            renderer->blendMode = SDL_BLENDMODE_NONE;
+        }
         return -1;
     }
 }
@@ -779,10 +789,20 @@ xrenderdrawcolor(SDL_Renderer *renderer)
 {
     // Premultiply the color channels as well as modulate them to a 16 bit color space
     XRenderColor xrender_color;
-    xrender_color.red = ((unsigned short)renderer->r + 1) * ((unsigned short)renderer->a + 1) - 1;
-    xrender_color.green = ((unsigned short)renderer->g + 1) * ((unsigned short)renderer->a + 1) - 1;
-    xrender_color.blue = ((unsigned short)renderer->b + 1) * ((unsigned short)renderer->a + 1) - 1;
-    xrender_color.alpha = ((unsigned short)renderer->a + 1) * ((unsigned short)renderer->a + 1) - 1;
+    double alphad;
+    if(renderer->blendMode == SDL_BLENDMODE_NONE)
+        alphad = 1.0;
+    else
+        alphad = (renderer->a) / 255.0;
+
+    xrender_color.alpha = (unsigned short) (alphad * 0xFFFF);
+
+    xrender_color.red =
+        (unsigned short) ((renderer->r / 255.0) * alphad * 0xFFFF);
+    xrender_color.green =
+        (unsigned short) ((renderer->g / 255.0) * alphad * 0xFFFF);
+    xrender_color.blue =
+        (unsigned short) ((renderer->b / 255.0) * alphad * 0xFFFF);
     return xrender_color;
 }
 
@@ -1050,6 +1070,12 @@ X11_RenderDrawRects(SDL_Renderer * renderer, const SDL_Rect ** rects, int count)
     XRectangle *xrects, *xrect;
     xrect = xrects = SDL_stack_alloc(XRectangle, count);
     xcount = 0;
+    
+    clip.x = 0;
+    clip.y = 0;
+    clip.w = window->w;
+    clip.h = window->h;
+
     for (i = 0; i < count; ++i) {
         if (!SDL_IntersectRect(rects[i], &clip, &rect)) {
             continue;
@@ -1066,11 +1092,7 @@ X11_RenderDrawRects(SDL_Renderer * renderer, const SDL_Rect ** rects, int count)
             SDL_AddDirtyRect(&data->dirty, &rect);
         }
     }
-    clip.x = 0;
-    clip.y = 0;
-    clip.w = window->w;
-    clip.h = window->h;
-
+     
 #ifdef SDL_VIDEO_DRIVER_X11_XRENDER
     if(data->use_xrender == SDL_TRUE) {
         XRenderColor foreground;
@@ -1151,7 +1173,6 @@ X11_RenderFillRects(SDL_Renderer * renderer, const SDL_Rect ** rects, int count)
         unsigned long valuemask;
 
         foreground = xrenderdrawcolor(renderer);
-        attributes.clip_mask = data->mask;
         valuemask = CPClipMask;
         attributes.clip_mask = data->mask;
         
@@ -1424,15 +1445,9 @@ X11_RenderPresent(SDL_Renderer * renderer)
 #ifdef SDL_VIDEO_DRIVER_X11_XRENDER
             if(data->use_xrender == SDL_TRUE)
             {
-                if(renderer->blendMode == SDL_BLENDMODE_MASK)
-                    XRenderComposite(data->display, data->blend_op, data->drawable_pict,
-                                     data->drawable_pict, data->xwindow_pict, rect->x, rect->y,
-                                     0, 0, rect->x, rect->y, rect->w, rect->h);
-                else
-                    XRenderComposite(data->display, data->blend_op, data->drawable_pict, None,
-                                     data->xwindow_pict, rect->x, rect->y, 0, 0, rect->x, rect->y,
-                                     rect->w, rect->h);
-
+                XRenderComposite(data->display, PictOpOver, data->drawable_pict, None,
+                                 data->xwindow_pict, rect->x, rect->y, 0, 0, rect->x, rect->y,
+                                 rect->w+1, rect->h+1);
             }
             else
 #endif

src/video/x11/SDL_x11window.c

@@ -513,6 +513,9 @@ X11_CreateWindow(_THIS, SDL_Window * window)
     } else {
         y = window->y;
     }
+#ifdef SDL_VIDEO_DRIVER_X11_XRENDER
+    xattr.background_pixel = 0xFF000000;
+#endif
 
     w = XCreateWindow(data->display,
                       RootWindow(data->display, displaydata->screen), x, y,