gdiplus: Support line gradient brushes in GdipFillPath.

dlls/gdiplus/graphics.c

@@ -172,6 +172,164 @@ static void transform_and_round_points(GpGraphics *graphics, POINT *pti,
     }
 }
 
+static ARGB blend_colors(ARGB start, ARGB end, int current, int total)
+{
+    ARGB result=0;
+    ARGB i;
+    for (i=0xff; i<=0xff0000; i = i << 8)
+        result |= (((start&i)*(total - current)+(end&i)*(current))/total)&i;
+    return result;
+}
+
+static void brush_fill_path(GpGraphics *graphics, GpBrush* brush)
+{
+    switch (brush->bt)
+    {
+    case BrushTypeLinearGradient:
+    {
+        GpLineGradient *line = (GpLineGradient*)brush;
+        RECT rc;
+        int num_steps = 255;
+
+        SelectClipPath(graphics->hdc, RGN_AND);
+        if (GetClipBox(graphics->hdc, &rc) != NULLREGION)
+        {
+            GpPointF endpointsf[2];
+            POINT endpointsi[2];
+            POINT poly[4];
+
+            SelectObject(graphics->hdc, GetStockObject(NULL_PEN));
+
+            /* fill with starting color */
+            FillRect(graphics->hdc, &rc, brush->gdibrush);
+
+            endpointsf[0] = line->startpoint;
+            endpointsf[1] = line->endpoint;
+            transform_and_round_points(graphics, endpointsi, endpointsf, 2);
+
+            if (abs(endpointsi[0].x-endpointsi[1].x) > abs(endpointsi[0].y-endpointsi[1].y))
+            {
+                /* vertical-ish gradient */
+                int endborderx; /* vertical rectangle boundary near endpoint */
+                int startx, endx; /* x co-ordinates of endpoints shifted to intersect the top of the visible rectangle */
+                int startbottomx, endbottomx; /* x co-ordinate of endpoints shifted to intersect the bottom of the visible rectangle */
+                int width;
+                COLORREF col;
+                HBRUSH hbrush, hprevbrush;
+                int i;
+
+                if (endpointsi[1].x > endpointsi[0].x)
+                    endborderx = rc.right;
+                else
+                    endborderx = rc.left;
+
+                startx = roundr((rc.top - endpointsf[0].Y) * (endpointsf[1].Y - endpointsf[0].Y) / (endpointsf[0].X - endpointsf[1].X) + endpointsf[0].X);
+                endx = roundr((rc.top - endpointsf[1].Y) * (endpointsf[1].Y - endpointsf[0].Y) / (endpointsf[0].X - endpointsf[1].X) + endpointsf[1].X);
+                width = endx - startx;
+                startbottomx = roundr((rc.bottom - endpointsf[0].Y) * (endpointsf[1].Y - endpointsf[0].Y) / (endpointsf[0].X - endpointsf[1].X) + endpointsf[0].X);
+                endbottomx = startbottomx+width;
+
+                if (num_steps > abs(width)) num_steps = abs(width);
+
+                poly[0].x = endborderx;
+                poly[0].y = rc.bottom;
+                poly[1].x = endborderx;
+                poly[1].y = rc.top;
+                poly[2].y = rc.top;
+                poly[3].y = rc.bottom;
+
+                for (i=1; i<num_steps; i++)
+                {
+                    ARGB argb = blend_colors(line->startcolor, line->endcolor, i, num_steps);
+                    int ofs = width * i / num_steps;
+                    col = ARGB2COLORREF(argb);
+                    hbrush = CreateSolidBrush(col);
+                    hprevbrush = SelectObject(graphics->hdc, hbrush);
+                    poly[2].x = startx + ofs;
+                    poly[3].x = startbottomx + ofs;
+                    Polygon(graphics->hdc, poly, 4);
+                    SelectObject(graphics->hdc, hprevbrush);
+                    DeleteObject(hbrush);
+                }
+
+                poly[2].x = endx;
+                poly[3].x = endbottomx;
+
+                /* draw the ending color */
+                col = ARGB2COLORREF(line->endcolor);
+                hbrush = CreateSolidBrush(col);
+                hprevbrush = SelectObject(graphics->hdc, hbrush);
+                Polygon(graphics->hdc, poly, 4);
+                SelectObject(graphics->hdc, hprevbrush);
+                DeleteObject(hbrush);
+            }
+            else if (endpointsi[0].y != endpointsi[1].y)
+            {
+                /* horizontal-ish gradient */
+                int endbordery; /* horizontal rectangle boundary near endpoint */
+                int starty, endy; /* y co-ordinates of endpoints shifted to intersect the left of the visible rectangle */
+                int startrighty, endrighty; /* y co-ordinate of endpoints shifted to intersect the right of the visible rectangle */
+                int height;
+                COLORREF col;
+                HBRUSH hbrush, hprevbrush;
+                int i;
+
+                if (endpointsi[1].y > endpointsi[0].y)
+                    endbordery = rc.bottom;
+                else
+                    endbordery = rc.top;
+
+                starty = roundr((rc.left - endpointsf[0].X) * (endpointsf[0].X - endpointsf[1].X) / (endpointsf[1].Y - endpointsf[0].Y) + endpointsf[0].Y);
+                endy = roundr((rc.left - endpointsf[1].X) * (endpointsf[0].X - endpointsf[1].X) / (endpointsf[1].Y - endpointsf[0].Y) + endpointsf[1].Y);
+                height = endy - starty;
+                startrighty = roundr((rc.right - endpointsf[0].X) * (endpointsf[0].X - endpointsf[1].X) / (endpointsf[1].Y - endpointsf[0].Y) + endpointsf[0].Y);
+                endrighty = startrighty+height;
+
+                if (num_steps > abs(height)) num_steps = abs(height);
+
+                poly[0].x = rc.right;
+                poly[0].y = endbordery;
+                poly[1].x = rc.left;
+                poly[1].y = endbordery;
+                poly[2].x = rc.left;
+                poly[3].x = rc.right;
+
+                for (i=1; i<num_steps; i++)
+                {
+                    ARGB argb = blend_colors(line->startcolor, line->endcolor, i, num_steps);
+                    int ofs = height * i / num_steps;
+                    col = ARGB2COLORREF(argb);
+                    hbrush = CreateSolidBrush(col);
+                    hprevbrush = SelectObject(graphics->hdc, hbrush);
+                    poly[2].y = starty + ofs;
+                    poly[3].y = startrighty + ofs;
+                    Polygon(graphics->hdc, poly, 4);
+                    SelectObject(graphics->hdc, hprevbrush);
+                    DeleteObject(hbrush);
+                }
+
+                poly[2].y = endy;
+                poly[3].y = endrighty;
+
+                /* draw the ending color */
+                col = ARGB2COLORREF(line->endcolor);
+                hbrush = CreateSolidBrush(col);
+                hprevbrush = SelectObject(graphics->hdc, hbrush);
+                Polygon(graphics->hdc, poly, 4);
+                SelectObject(graphics->hdc, hprevbrush);
+                DeleteObject(hbrush);
+            }
+            /* else startpoint == endpoint */
+        }
+        break;
+    }
+    default:
+        SelectObject(graphics->hdc, brush->gdibrush);
+        FillPath(graphics->hdc);
+        break;
+    }
+}
+
 /* GdipDrawPie/GdipFillPie helper function */
 static void draw_pie(GpGraphics *graphics, REAL x, REAL y, REAL width,
     REAL height, REAL startAngle, REAL sweepAngle)
@@ -2086,7 +2244,6 @@ GpStatus WINGDIPAPI GdipFillPath(GpGraphics *graphics, GpBrush *brush, GpPath *p
 
     save_state = SaveDC(graphics->hdc);
     EndPath(graphics->hdc);
-    SelectObject(graphics->hdc, brush->gdibrush);
     SetPolyFillMode(graphics->hdc, (path->fill == FillModeAlternate ? ALTERNATE
                                                                     : WINDING));
 
@@ -2098,7 +2255,7 @@ GpStatus WINGDIPAPI GdipFillPath(GpGraphics *graphics, GpBrush *brush, GpPath *p
         goto end;
 
     EndPath(graphics->hdc);
-    FillPath(graphics->hdc);
+    brush_fill_path(graphics, brush);
 
     retval = Ok;