[PATCH v2] winex11: Fix off-by-one errors in color value scaling

[Alex Henrie]

Signed-off-by: Alex Henrie <alexhenrie24 at gmail.com>
---
For 0 to map to 0 and 255 to map to 65535, the value must be multiplied
by 257, not 256. The incorrect factor would cause the color #FFFFFF to
become #FEFEFE.

v2: Also correct reverse mapping
---
 dlls/winex11.drv/palette.c | 42 ++++++++++++++++++++------------------
 1 file changed, 22 insertions(+), 20 deletions(-)

diff --git a/dlls/winex11.drv/palette.c b/dlls/winex11.drv/palette.c
index 25bdb5f2bf..06d02c300a 100644
--- a/dlls/winex11.drv/palette.c
+++ b/dlls/winex11.drv/palette.c
@@ -293,19 +293,19 @@ static BOOL X11DRV_PALETTE_BuildPrivateMap( const PALETTEENTRY *sys_pal_template
     {
        if( i < NB_RESERVED_COLORS/2 )
        {
-         color.red   = sys_pal_template[i].peRed * 65535 / 255;
-         color.green = sys_pal_template[i].peGreen * 65535 / 255;
-         color.blue  = sys_pal_template[i].peBlue * 65535 / 255;
-	 COLOR_sysPal[i] = sys_pal_template[i];
+         color.red   = sys_pal_template[i].peRed * (65535 / 255);
+         color.green = sys_pal_template[i].peGreen * (65535 / 255);
+         color.blue  = sys_pal_template[i].peBlue * (65535 / 255);
+         COLOR_sysPal[i] = sys_pal_template[i];
          COLOR_sysPal[i].peFlags |= PC_SYS_USED;
        }
        else if( i >= palette_size - NB_RESERVED_COLORS/2 )
        {
-	 int j = NB_RESERVED_COLORS + i - palette_size;
-         color.red   = sys_pal_template[j].peRed * 65535 / 255;
-         color.green = sys_pal_template[j].peGreen * 65535 / 255;
-         color.blue  = sys_pal_template[j].peBlue * 65535 / 255;
-	 COLOR_sysPal[i] = sys_pal_template[j];
+         int j = NB_RESERVED_COLORS + i - palette_size;
+         color.red   = sys_pal_template[j].peRed * (65535 / 255);
+         color.green = sys_pal_template[j].peGreen * (65535 / 255);
+         color.blue  = sys_pal_template[j].peBlue * (65535 / 255);
+         COLOR_sysPal[i] = sys_pal_template[j];
          COLOR_sysPal[i].peFlags |= PC_SYS_USED;
        }
 
@@ -405,9 +405,9 @@ static BOOL X11DRV_PALETTE_BuildSharedMap( const PALETTEENTRY *sys_pal_template
 	     for( c.pixel = 0, diff = 0x7fffffff; c.pixel < max; c.pixel += step )
 	     {
 		XQueryColor(gdi_display, default_colormap, &c);
-		r = (c.red - color.red)>>8;
-		g = (c.green - color.green)>>8;
-		b = (c.blue - color.blue)>>8;
+		r = (c.red - color.red) / (65535 / 255);
+		g = (c.green - color.green) / (65535 / 255);
+		b = (c.blue - color.blue) / (65535 / 255);
 		r = r*r + g*g + b*b;
 		if( r < diff ) { best = c; diff = r; }
 	     }
@@ -633,9 +633,9 @@ static void X11DRV_PALETTE_FillDefaultColors( const PALETTEENTRY *sys_pal_templa
 	 {
 	   XColor color;
 	   color.pixel = (X11DRV_PALETTE_PaletteToXPixel)? X11DRV_PALETTE_PaletteToXPixel[idx] : idx;
-	   color.red = COLOR_sysPal[idx].peRed << 8;
-	   color.green = COLOR_sysPal[idx].peGreen << 8;
-	   color.blue =  COLOR_sysPal[idx].peBlue << 8;
+	   color.red = COLOR_sysPal[idx].peRed * (65535 / 255);
+	   color.green = COLOR_sysPal[idx].peGreen * (65535 / 255);
+	   color.blue = COLOR_sysPal[idx].peBlue * (65535 / 255);
 	   color.flags = DoRed | DoGreen | DoBlue;
 	   XStoreColor(gdi_display, default_colormap, &color);
 	 }
@@ -658,7 +658,9 @@ static void X11DRV_PALETTE_FillDefaultColors( const PALETTEENTRY *sys_pal_templa
 	  xc.pixel = i;
 
 	  XQueryColor(gdi_display, default_colormap, &xc);
-	  r = xc.red>>8; g = xc.green>>8; b = xc.blue>>8;
+	  r = xc.red / (65535 / 255);
+	  g = xc.green / (65535 / 255);
+	  b = xc.blue / (65535 / 255);
 
 	  if( xc.pixel < 256 && X11DRV_PALETTE_CheckSysColor( sys_pal_template, RGB(r, g, b)) &&
 	      XAllocColor(gdi_display, default_colormap, &xc) )
@@ -753,7 +755,7 @@ COLORREF X11DRV_PALETTE_ToLogical(X11DRV_PDEVICE *physDev, int pixel)
 
     color.pixel = pixel;
     XQueryColor(gdi_display, default_colormap, &color);
-    return RGB(color.red >> 8, color.green >> 8, color.blue >> 8);
+    return RGB(color.red / (65535 / 255), color.green / (65535 / 255), color.blue / (65535 / 255));
 }
 
 
@@ -1156,9 +1158,9 @@ UINT CDECL X11DRV_RealizePalette( PHYSDEV dev, HPALETTE hpal, BOOL primary )
                     X11DRV_PALETTE_firstFree = X11DRV_PALETTE_freeList[index];
 
                     color.pixel = (X11DRV_PALETTE_PaletteToXPixel) ? X11DRV_PALETTE_PaletteToXPixel[index] : index;
-                    color.red = entries[i].peRed << 8;
-                    color.green = entries[i].peGreen << 8;
-                    color.blue = entries[i].peBlue << 8;
+                    color.red = entries[i].peRed * (65535 / 255);
+                    color.green = entries[i].peGreen * (65535 / 255);
+                    color.blue = entries[i].peBlue * (65535 / 255);
                     color.flags = DoRed | DoGreen | DoBlue;
                     XStoreColor(gdi_display, default_colormap, &color);
 
-- 
2.24.0