3 files changed, 16 insertions, 16 deletions
diff --git a/src/drv/cdgl.c b/src/drv/cdgl.c
index 4357e5a..fb1739d 100644
--- a/src/drv/cdgl.c
+++ b/src/drv/cdgl.c
@@ -638,10 +638,11 @@ static long int cdforeground(cdCtxCanvas *ctxcanvas, long int color)
 
 static void cdclear(cdCtxCanvas* ctxcanvas)
 {
-  unsigned char r, g, b;
+  unsigned char r, g, b, a;
   cdDecodeColor(ctxcanvas->canvas->background, &r, &g, &b);
-  glClearColor((GLclampf)((double)r/255.0), (GLclampf)((double)g/255.0), (GLclampf)((double)b/255.0), 0);
-  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+  a = cdDecodeAlpha(ctxcanvas->canvas->background);
+  glClearColor((GLclampf)r/255.0f, (GLclampf)g/255.0f, (GLclampf)b/255.0f, (GLclampf)a/255.0f);
+  glClear(GL_COLOR_BUFFER_BIT);
 }
 
 static void cdfline(cdCtxCanvas *ctxcanvas, double x1, double y1, double x2, double y2)
diff --git a/src/drv/cdirgb.c b/src/drv/cdirgb.c
index 68a5766..d9dd6a8 100644
--- a/src/drv/cdirgb.c
+++ b/src/drv/cdirgb.c
@@ -430,7 +430,8 @@ static void cdclear(cdCtxCanvas* ctxcanvas)
   memset(ctxcanvas->red, cdRed(ctxcanvas->canvas->background), size);
   memset(ctxcanvas->green, cdGreen(ctxcanvas->canvas->background), size);
   memset(ctxcanvas->blue, cdBlue(ctxcanvas->canvas->background), size);
-  if (ctxcanvas->alpha) memset(ctxcanvas->alpha, cdAlpha(ctxcanvas->canvas->background), size);  /* here is the normal alpha coding */
+  if (ctxcanvas->alpha) 
+    memset(ctxcanvas->alpha, cdAlpha(ctxcanvas->canvas->background), size);  /* here is the normal alpha coding */
 }
 
 static void irgPostProcessIntersect(unsigned char* clip, int size)
diff --git a/src/gdiplus/cdwinp.cpp b/src/gdiplus/cdwinp.cpp
index db09cd6..522f136 100644
--- a/src/gdiplus/cdwinp.cpp
+++ b/src/gdiplus/cdwinp.cpp
@@ -139,9 +139,7 @@ static void sUpdateFillBrush(cdCtxCanvas* ctxcanvas)
     {
       // only stipple depends on Foreground and Background Color.
       if (ctxcanvas->canvas->interior_style == CD_STIPPLE)
-      {
         cdstipple(ctxcanvas, ctxcanvas->canvas->stipple_w, ctxcanvas->canvas->stipple_h, ctxcanvas->canvas->stipple);
-      }
       break;
     }
   }
@@ -158,18 +156,17 @@ static long int cdforeground(cdCtxCanvas* ctxcanvas, long int color)
   return color;
 }
 
-static Color sSetAlpha(const Color& c, BYTE alpha)
+static Color sTranspAlpha(const Color& c)
 {
-  return Color(alpha, c.GetRed(), c.GetGreen(), c.GetBlue());
+  return Color(0, c.GetRed(), c.GetGreen(), c.GetBlue());
 }
 
 static long int cdbackground(cdCtxCanvas* ctxcanvas, long int color)
 {
   ctxcanvas->bg = sColor2Windows(color);
 
-  if ((ctxcanvas->canvas->back_opacity == CD_TRANSPARENT) &&
-    (cdAlpha(ctxcanvas->canvas->background) == 255)) 
-    ctxcanvas->bg = sSetAlpha(ctxcanvas->bg, (BYTE)0);
+  if (ctxcanvas->canvas->back_opacity == CD_TRANSPARENT) 
+    ctxcanvas->bg = sTranspAlpha(ctxcanvas->bg);  /* set background as full transparent */
 
   sUpdateFillBrush(ctxcanvas);
 
@@ -181,10 +178,10 @@ static int cdbackopacity(cdCtxCanvas* ctxcanvas, int opacity)
   switch (opacity)
   {
   case CD_TRANSPARENT:
-    ctxcanvas->bg = sSetAlpha(ctxcanvas->bg, (BYTE)0);
+    ctxcanvas->bg = sTranspAlpha(ctxcanvas->bg);  /* set background as full transparent */
     break;
   case CD_OPAQUE:
-    ctxcanvas->bg = sSetAlpha(ctxcanvas->bg, (BYTE)255);
+    ctxcanvas->bg = sColor2Windows(ctxcanvas->canvas->background);
     break;
   }
 
@@ -1619,7 +1616,8 @@ static void cdclear(cdCtxCanvas* ctxcanvas)
   if (ctxcanvas->canvas->clip_mode != CD_CLIPOFF) 
     ctxcanvas->graphics->ResetClip();
   
-  ctxcanvas->graphics->Clear(sSetAlpha(ctxcanvas->bg, (BYTE)255));
+  /* do NOT use "ctxcanvas->bg" here, because it depends on backopacity */
+  ctxcanvas->graphics->Clear(sColor2Windows(ctxcanvas->canvas->background));
   
   if (ctxcanvas->canvas->clip_mode != CD_CLIPOFF) 
     cdclip(ctxcanvas, ctxcanvas->canvas->clip_mode);
@@ -2717,8 +2715,8 @@ cdCtxCanvas *cdwpCreateCanvas(cdCanvas* canvas, Graphics* graphics, int wtype)
 
   set_aa_attrib(ctxcanvas, "1");  // default is ANTIALIAS=1
 
-  ctxcanvas->fg = Color(); // black
-  ctxcanvas->bg = Color(255, 255, 255); // white
+  ctxcanvas->fg = Color(); // black,opaque
+  ctxcanvas->bg = Color(255, 255, 255); // white,opaque => used only for fill
 
   canvas->invert_yaxis = 1;