Fixed shadow offset on edges

I now adjust the viewport and icrease the shadowbuffer size
to make it possible to draw shadows on objects outside the edge
when using offsets.

2 files changed, 38 insertions, 28 deletions

diff --git a/src/context2d.cpp b/src/context2d.cpp
index bc3c77b..0ae52b8 100644
--- a/src/context2d.cpp
+++ b/src/context2d.cpp
@@ -446,37 +446,51 @@ void Context2D::setMiterLimit(qreal m)
 
 void Context2D::setShadowOffsetX(qreal x)
 {
+    if (m_state.shadowOffsetX == x)
+        return;
+    m_state.shadowOffsetX = x;
+    updateShadowBuffer();
     if (m_painter.device() == &m_shadowbuffer && m_state.shadowBlur>0)
         endPainting();
-    m_state.shadowOffsetX = x;
     m_state.flags |= DirtyShadowOffsetX;
 }
 
+void Context2D::updateShadowBuffer() {
+    if (m_shadowbuffer.isNull() || m_shadowbuffer.width() != m_width+m_state.shadowOffsetX ||
+        m_shadowbuffer.height() != m_height+m_state.shadowOffsetY) {
+        m_shadowbuffer = QImage(m_width+m_state.shadowOffsetX, m_height+m_state.shadowOffsetY, QImage::Format_ARGB32);
+        m_shadowbuffer.fill(Qt::transparent);
+    }
+}
+
 void Context2D::setShadowOffsetY(qreal y)
 {
+    if (m_state.shadowOffsetY == y)
+        return;
+    m_state.shadowOffsetY = y;
+    updateShadowBuffer();
     if (m_painter.device() == &m_shadowbuffer && m_state.shadowBlur>0)
         endPainting();
-    m_state.shadowOffsetY = y;
+
     m_state.flags |= DirtyShadowOffsetY;
 }
 
 void Context2D::setShadowBlur(qreal b)
 {
-    if (m_shadowbuffer.isNull() || m_shadowbuffer.width() != m_width || m_shadowbuffer.height() != m_height) {
-        m_shadowbuffer = QImage(m_width, m_height, QImage::Format_ARGB32);
-    }
-
+    if (m_state.shadowBlur == b)
+        return;
+    m_state.shadowBlur = b;
+    updateShadowBuffer();
     if (m_painter.device() == &m_shadowbuffer && m_state.shadowBlur>0)
         endPainting();
-    m_state.shadowBlur = b;
     m_state.flags |= DirtyShadowBlur;
 }
 
 void Context2D::setShadowColor(const QString &str)
 {
+    m_state.shadowColor = colorFromString(str);
     if (m_painter.device() == &m_shadowbuffer && m_state.shadowBlur>0)
         endPainting();
-    m_state.shadowColor = colorFromString(str);
     m_state.flags |= DirtyShadowColor;
 }
 
@@ -921,19 +935,20 @@ void Context2D::beginPainting()
         m_pixmap.fill(parent()->property("color").value<QColor>());
     }
 
-    if (m_state.shadowBlur > 0) {
-        if (m_shadowbuffer.width() != m_width || m_shadowbuffer.height() != m_height) {
-            m_shadowbuffer = QImage(m_width, m_height, QImage::Format_ARGB32_Premultiplied);
-        }
+    if (m_state.shadowBlur > 0 && m_painter.device() != &m_shadowbuffer) {
+        if (m_painter.isActive())
+            m_painter.end();
+        updateShadowBuffer();
+        m_painter.begin(&m_shadowbuffer);
+        m_painter.setViewport(m_state.shadowOffsetX,
+                              m_state.shadowOffsetY,
+                              m_shadowbuffer.width(),
+                              m_shadowbuffer.height());
+        m_shadowbuffer.fill(Qt::transparent);
     }
 
     if (!m_painter.isActive()) {
-        if (m_state.shadowBlur == 0) {
-            m_painter.begin(&m_pixmap);
-        } else {
-            m_shadowbuffer.fill(Qt::transparent);
-            m_painter.begin(&m_shadowbuffer);
-        }
+        m_painter.begin(&m_pixmap);
         m_painter.setRenderHint(QPainter::Antialiasing);
         if (!m_state.clipPath.isEmpty())
             m_painter.setClipPath(m_state.clipPath);
@@ -949,13 +964,6 @@ void Context2D::beginPainting()
         pen.setMiterLimit(m_state.miterLimit);
         m_painter.setPen(pen);
     } else {
-        if (m_state.shadowBlur > 0 && m_painter.device() != &m_shadowbuffer) {
-            m_painter.end();
-
-
-            m_shadowbuffer.fill(Qt::transparent);
-            m_painter.begin(&m_shadowbuffer);
-        }
         setupPainter();
         m_state.flags = 0;
     }
@@ -987,17 +995,18 @@ void Context2D::endPainting()
             m_painter.end();
 
         m_painter.begin(&m_pixmap);
-        setupPainter();
 
         // draw the blurred drop shadow...
+        m_painter.save();
         QTransform tf = m_painter.transform();
         m_painter.translate(0, imageRect.height());
         m_painter.rotate(-90);
-        m_painter.drawImage(-m_state.shadowOffsetY, m_state.shadowOffsetX, alphaChannel);
+        m_painter.drawImage(0, 0, alphaChannel);
         m_painter.setTransform(tf);
+        m_painter.restore();
 
         // draw source
-        m_painter.drawImage(0, 0, m_shadowbuffer.copy());
+        m_painter.drawImage(-m_state.shadowOffsetX, -m_state.shadowOffsetY, m_shadowbuffer.copy());
         m_painter.end();
     }
 }
diff --git a/src/context2d.h b/src/context2d.h
index 57cf922..e700901 100644
--- a/src/context2d.h
+++ b/src/context2d.h
@@ -244,6 +244,7 @@ signals:
 private:
     void setupPainter();
     void beginPainting();
+    void updateShadowBuffer();
 
     int m_changeTimerId;
     QPainterPath m_path;