Use transparency for gradients fdo#45219

vclcanvas has 1bpp alpha - so cut-off transparency at 98%
This looks for all practical cases close enough to full alpha.

(cherry picked from commit 3f5efa1e76e187070d412d102e4c057679065bcc)

Signed-off-by: Tor Lillqvist <tlillqvist@suse.com>

2 files changed, 42 insertions, 41 deletions

diff --git a/canvas/source/vcl/canvashelper.cxx b/canvas/source/vcl/canvashelper.cxx
index 5d4c40a31ceb..3649ccf88bb9 100644
--- a/canvas/source/vcl/canvashelper.cxx
+++ b/canvas/source/vcl/canvashelper.cxx
@@ -155,8 +155,9 @@ namespace vclcanvas
             tools::OutDevStateKeeper aStateKeeper( mpProtectedOutDev );
 
             rOutDev.EnableMapMode( sal_False );
-            rOutDev.SetLineColor( COL_TRANSPARENT );
-            rOutDev.SetFillColor( COL_TRANSPARENT );
+            rOutDev.SetLineColor( COL_WHITE );
+            rOutDev.SetFillColor( COL_WHITE );
+            rOutDev.SetClipRegion();
             rOutDev.DrawRect( Rectangle( Point(),
                                          rOutDev.GetOutputSizePixel()) );
 
@@ -166,8 +167,9 @@ namespace vclcanvas
 
                 rOutDev2.SetDrawMode( DRAWMODE_DEFAULT );
                 rOutDev2.EnableMapMode( sal_False );
-                rOutDev2.SetLineColor( COL_TRANSPARENT );
-                rOutDev2.SetFillColor( COL_TRANSPARENT );
+                rOutDev2.SetLineColor( COL_WHITE );
+                rOutDev2.SetFillColor( COL_WHITE );
+                rOutDev2.SetClipRegion();
                 rOutDev2.DrawRect( Rectangle( Point(),
                                               rOutDev2.GetOutputSizePixel()) );
                 rOutDev2.SetDrawMode( DRAWMODE_BLACKLINE | DRAWMODE_BLACKFILL | DRAWMODE_BLACKTEXT |
@@ -500,19 +502,11 @@ namespace vclcanvas
 
             if( mp2ndOutDev )
             {
-                // HACK. Normally, CanvasHelper does not care
-                // about actually what mp2ndOutDev is...
-                // well, here we do & assume a 1bpp target.
-                if( nTransparency > 127 )
-                {
-                    mp2ndOutDev->getOutDev().SetDrawMode( DRAWMODE_WHITELINE | DRAWMODE_WHITEFILL | DRAWMODE_WHITETEXT |
-                                                          DRAWMODE_WHITEGRADIENT | DRAWMODE_WHITEBITMAP );
-                    mp2ndOutDev->getOutDev().SetFillColor( COL_WHITE );
-                    mp2ndOutDev->getOutDev().DrawPolyPolygon( aPolyPoly );
-                    mp2ndOutDev->getOutDev().SetDrawMode( DRAWMODE_BLACKLINE | DRAWMODE_BLACKFILL | DRAWMODE_BLACKTEXT |
-                                                          DRAWMODE_BLACKGRADIENT | DRAWMODE_BLACKBITMAP );
-                }
-                else
+                // HACK. Normally, CanvasHelper does not care about
+                // actually what mp2ndOutDev is...  well, here we do &
+                // assume a 1bpp target - everything beyond 97%
+                // transparency is fully transparent
+                if( nTransparency < 253 )
                 {
                     mp2ndOutDev->getOutDev().DrawPolyPolygon( aPolyPoly );
                 }
@@ -715,8 +709,25 @@ namespace vclcanvas
                                                     aBmpEx );
 
                 if( mp2ndOutDev )
+                {
+                    // HACK. Normally, CanvasHelper does not care about
+                    // actually what mp2ndOutDev is...  well, here we do &
+                    // assume a 1bpp target - everything beyond 97%
+                    // transparency is fully transparent
+                    if( aBmpEx.IsAlpha() )
+                    {
+                        Bitmap aMask( aBmpEx.GetAlpha().GetBitmap() );
+                        aMask.MakeMono( 253 );
+                        aBmpEx = BitmapEx( aBmpEx.GetBitmap(), aMask );
+                    }
+                    else if( aBmpEx.IsTransparent() )
+                    {
+                        aBmpEx = BitmapEx( aBmpEx.GetBitmap(), aBmpEx.GetMask() );
+                    }
+
                     mp2ndOutDev->getOutDev().DrawBitmapEx( ::vcl::unotools::pointFromB2DPoint( aOutputPos ),
                                                            aBmpEx );
+                }
 
                 // Returning a cache object is not useful, the XBitmap
                 // itself serves this purpose
diff --git a/canvas/source/vcl/canvashelper_texturefill.cxx b/canvas/source/vcl/canvashelper_texturefill.cxx
index 325d2b6271bd..3811ebd2b021 100644
--- a/canvas/source/vcl/canvashelper_texturefill.cxx
+++ b/canvas/source/vcl/canvashelper_texturefill.cxx
@@ -555,8 +555,6 @@ namespace vclcanvas
                            const rendering::Texture&                       texture,
                            int                                             nTransparency )
         {
-            (void)nTransparency;
-
             // TODO(T2): It is maybe necessary to lock here, should
             // maGradientPoly someday cease to be const. But then, beware of
             // deadlocks, canvashelper calls this method with locked own
@@ -606,18 +604,14 @@ namespace vclcanvas
                                 false );
                 rOutDev.Pop();
 
-                if( p2ndOutDev )
+                if( p2ndOutDev && nTransparency < 253 )
                 {
-                    p2ndOutDev->Push( PUSH_CLIPREGION );
-                    p2ndOutDev->IntersectClipRegion( aPolygonDeviceRectOrig );
-                    doGradientFill( *p2ndOutDev,
-                                    rValues,
-                                    rColors,
-                                    aTotalTransform,
-                                    aPolygonDeviceRectOrig,
-                                    nStepCount,
-                                    false );
-                    p2ndOutDev->Pop();
+                    // HACK. Normally, CanvasHelper does not care about
+                    // actually what mp2ndOutDev is...  well, here we do &
+                    // assume a 1bpp target - everything beyond 97%
+                    // transparency is fully transparent
+                    p2ndOutDev->SetFillColor( COL_BLACK );
+                    p2ndOutDev->DrawRect( aPolygonDeviceRectOrig );
                 }
             }
             else
@@ -637,18 +631,14 @@ namespace vclcanvas
                                 false );
                 rOutDev.Pop();
 
-                if( p2ndOutDev )
+                if( p2ndOutDev && nTransparency < 253 )
                 {
-                    p2ndOutDev->Push( PUSH_CLIPREGION );
-                    p2ndOutDev->SetClipRegion( aPolyClipRegion );
-                    doGradientFill( *p2ndOutDev,
-                                    rValues,
-                                    rColors,
-                                    aTotalTransform,
-                                    aPolygonDeviceRectOrig,
-                                    nStepCount,
-                                    false );
-                    p2ndOutDev->Pop();
+                    // HACK. Normally, CanvasHelper does not care about
+                    // actually what mp2ndOutDev is...  well, here we do &
+                    // assume a 1bpp target - everything beyond 97%
+                    // transparency is fully transparent
+                    p2ndOutDev->SetFillColor( COL_BLACK );
+                    p2ndOutDev->DrawPolyPolygon( rPoly );
                 }
             }
 #else // TODO: remove once doing the XOR-trick in the canvas-layer becomes redundant