Fix dotted line drawing for GDI device driver

When GDI device driver draws a dotted line, it also clip the line
into the device context's bound before drawing. This CL includes
a couple fixes:

-- When this driver is used for EMF drawing, the drawing is not
bound to the device context so clipping is not needed;
-- Transformation needs to be applied before clipping since the
transformation may move the line into the bound;
-- While checking for out-of-bound flags, bit operations are needed
to make sure the discarded line is completely out of bound, not
partially inside the bound;

BUG=chromium:539533

Review-Url: https://codereview.chromium.org/2562533002

2 files changed, 42 insertions, 39 deletions

diff --git a/core/fxge/win32/fx_win32_device.cpp b/core/fxge/win32/fx_win32_device.cpp
index e0d2e60a15..2746587be2 100644
--- a/core/fxge/win32/fx_win32_device.cpp
+++ b/core/fxge/win32/fx_win32_device.cpp
@@ -738,7 +738,9 @@ CGdiDeviceDriver::CGdiDeviceDriver(HDC hDC, int device_class) {
   CWin32Platform* pPlatform =
       (CWin32Platform*)CFX_GEModule::Get()->GetPlatformData();
   SetStretchBltMode(hDC, pPlatform->m_bHalfTone ? HALFTONE : COLORONCOLOR);
-  if (GetObjectType(m_hDC) == OBJ_MEMDC) {
+  DWORD obj_type = GetObjectType(m_hDC);
+  m_bMetafileDCType = obj_type == OBJ_ENHMETADC || obj_type == OBJ_ENHMETAFILE;
+  if (obj_type == OBJ_MEMDC) {
     HBITMAP hBitmap = CreateBitmap(1, 1, 1, 1, nullptr);
     hBitmap = (HBITMAP)SelectObject(m_hDC, hBitmap);
     BITMAP bitmap;
@@ -940,45 +942,45 @@ void* CGdiDeviceDriver::GetPlatformSurface() const {
 void CGdiDeviceDriver::DrawLine(FX_FLOAT x1,
                                 FX_FLOAT y1,
                                 FX_FLOAT x2,
-                                FX_FLOAT y2,
-                                const CFX_Matrix* pMatrix) {
-  bool bStartOutOfBounds = x1 < 0 || x1 > m_Width || y1 < 0 || y1 > m_Height;
-  bool bEndOutOfBounds = x2 < 0 || x2 > m_Width || y2 < 0 || y2 > m_Height;
-  if (bStartOutOfBounds & bEndOutOfBounds)
-    return;
+                                FX_FLOAT y2) {
+  if (!m_bMetafileDCType) {  // EMF drawing is not bound to the DC.
+    int startOutOfBoundsFlag = (x1 < 0) | ((x1 > m_Width) << 1) |
+                               ((y1 < 0) << 2) | ((y1 > m_Height) << 3);
+    int endOutOfBoundsFlag = (x2 < 0) | ((x2 > m_Width) << 1) |
+                             ((y2 < 0) << 2) | ((y2 > m_Height) << 3);
+    if (startOutOfBoundsFlag & endOutOfBoundsFlag)
+      return;
 
-  if (bStartOutOfBounds || bEndOutOfBounds) {
-    FX_FLOAT x[2];
-    FX_FLOAT y[2];
-    int np;
+    if (startOutOfBoundsFlag || endOutOfBoundsFlag) {
+      FX_FLOAT x[2];
+      FX_FLOAT y[2];
+      int np;
 #ifdef _SKIA_SUPPORT_
-    // TODO(caryclark) temporary replacement of antigrain in line function
-    // to permit removing antigrain altogether
-    rect_base rect = {0.0f, 0.0f, (FX_FLOAT)(m_Width), (FX_FLOAT)(m_Height)};
-    np = clip_liang_barsky(x1, y1, x2, y2, rect, x, y);
+      // TODO(caryclark) temporary replacement of antigrain in line function
+      // to permit removing antigrain altogether
+      rect_base rect = {0.0f, 0.0f, (FX_FLOAT)(m_Width), (FX_FLOAT)(m_Height)};
+      np = clip_liang_barsky(x1, y1, x2, y2, rect, x, y);
 #else
-    agg::rect_base<FX_FLOAT> rect(0.0f, 0.0f, (FX_FLOAT)(m_Width),
-                                  (FX_FLOAT)(m_Height));
-    np = agg::clip_liang_barsky<FX_FLOAT>(x1, y1, x2, y2, rect, x, y);
+      agg::rect_base<FX_FLOAT> rect(0.0f, 0.0f, (FX_FLOAT)(m_Width),
+                                    (FX_FLOAT)(m_Height));
+      np = agg::clip_liang_barsky<FX_FLOAT>(x1, y1, x2, y2, rect, x, y);
 #endif
-    if (np == 0)
-      return;
+      if (np == 0)
+        return;
 
-    if (np == 1) {
-      x2 = x[0];
-      y2 = y[0];
-    } else {
-      ASSERT(np == 2);
-      x1 = x[0];
-      y1 = y[0];
-      x2 = x[1];
-      y2 = y[1];
+      if (np == 1) {
+        x2 = x[0];
+        y2 = y[0];
+      } else {
+        ASSERT(np == 2);
+        x1 = x[0];
+        y1 = y[0];
+        x2 = x[1];
+        y2 = y[1];
+      }
     }
   }
-  if (pMatrix) {
-    pMatrix->Transform(x1, y1);
-    pMatrix->Transform(x2, y2);
-  }
+
   MoveToEx(m_hDC, FXSYS_round(x1), FXSYS_round(y1), nullptr);
   LineTo(m_hDC, FXSYS_round(x2), FXSYS_round(y2));
 }
@@ -1057,7 +1059,11 @@ bool CGdiDeviceDriver::DrawPath(const CFX_PathData* pPathData,
     FX_FLOAT y1 = pPathData->GetPointY(0);
     FX_FLOAT x2 = pPathData->GetPointX(1);
     FX_FLOAT y2 = pPathData->GetPointY(1);
-    DrawLine(x1, y1, x2, y2, pMatrix);
+    if (pMatrix) {
+      pMatrix->Transform(x1, y1);
+      pMatrix->Transform(x2, y2);
+    }
+    DrawLine(x1, y1, x2, y2);
   } else {
     SetPathToDC(m_hDC, pPathData, pMatrix);
     if (pGraphState && stroke_alpha) {
diff --git a/core/fxge/win32/win32_int.h b/core/fxge/win32/win32_int.h
index fa1cc6830e..ae090b72d3 100644
--- a/core/fxge/win32/win32_int.h
+++ b/core/fxge/win32/win32_int.h
@@ -152,11 +152,7 @@ class CGdiDeviceDriver : public IFX_RenderDeviceDriver {
   bool GetClipBox(FX_RECT* pRect) override;
   void* GetPlatformSurface() const override;
 
-  void DrawLine(FX_FLOAT x1,
-                FX_FLOAT y1,
-                FX_FLOAT x2,
-                FX_FLOAT y2,
-                const CFX_Matrix* pMatrix);
+  void DrawLine(FX_FLOAT x1, FX_FLOAT y1, FX_FLOAT x2, FX_FLOAT y2);
 
   bool GDI_SetDIBits(CFX_DIBitmap* pBitmap,
                      const FX_RECT* pSrcRect,
@@ -177,6 +173,7 @@ class CGdiDeviceDriver : public IFX_RenderDeviceDriver {
                           uint32_t flags);
 
   HDC m_hDC;
+  bool m_bMetafileDCType;
   int m_Width;
   int m_Height;
   int m_nBitsPerPixel;