try adding flag to allow lcd text even in a layer

BUG=skia:

Review URL: https://codereview.chromium.org/1513513002

gm/lcdtext.cpp

@@ -126,6 +126,33 @@ protected:
 private:
     typedef skiagm::GM INHERITED;
 };
-
 DEF_GM( return new LcdTextGM; )
 DEF_GM( return new LcdTextSizeGM; )
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
+
+DEF_SIMPLE_GM(savelayer_lcdtext, canvas, 620, 260) {
+    SkPaint paint;
+    paint.setAntiAlias(true);
+    paint.setLCDRenderText(true);
+    paint.setTextSize(20);
+
+    canvas->drawText("Hamburgefons", 12, 30, 30, paint);
+
+    const bool gPreserveLCDText[] = { false, true };
+
+    canvas->translate(0, 20);
+    for (auto preserve : gPreserveLCDText) {
+        preserve ? canvas->saveLayerPreserveLCDTextRequests(nullptr, nullptr)
+                 : canvas->saveLayer(nullptr, nullptr);
+        canvas->drawText("Hamburgefons", 12, 30, 60, paint);
+
+        SkPaint p;
+        p.setColor(0xFFCCCCCC);
+        canvas->drawRect(SkRect::MakeLTRB(25, 70, 200, 100), p);
+        canvas->drawText("Hamburgefons", 12, 30, 90, paint);
+
+        canvas->restore();
+        canvas->translate(0, 80);
+    }
+}

include/core/SkCanvas.h

@@ -336,6 +336,13 @@ public:
         return this->saveLayer(&bounds, paint);
     }
 
+    /**
+     *  Temporary name.
+     *  Will allow any requests for LCD text to be respected, so the caller must be careful to
+     *  only draw on top of opaque sections of the layer to get good results.
+     */
+    int saveLayerPreserveLCDTextRequests(const SkRect* bounds, const SkPaint* paint);
+
     /** DEPRECATED - use saveLayer(const SkRect*, const SkPaint*) instead.
 
         This behaves the same as saveLayer(const SkRect*, const SkPaint*),
@@ -1316,6 +1323,11 @@ protected:
                         const SkImageFilter* imageFilter = NULL);
 
 private:
+    enum PrivateSaveFlags {
+        // These must not overlap the public flags.
+        kPreserveLCDText_PrivateSaveFlag = 1 << 5,
+    };
+
     enum ShaderOverrideOpacity {
         kNone_ShaderOverrideOpacity,        //!< there is no overriding shader (bitmap or image)
         kOpaque_ShaderOverrideOpacity,      //!< the overriding shader is opaque

include/core/SkDevice.h

@@ -333,16 +333,26 @@ protected:
                                           const SkPaint*);
 
     struct CreateInfo {
-        static SkPixelGeometry AdjustGeometry(const SkImageInfo&, TileUsage, SkPixelGeometry);
+        static SkPixelGeometry AdjustGeometry(const SkImageInfo&, TileUsage, SkPixelGeometry,
+                                              bool preserveLCDText);
 
         // The constructor may change the pixel geometry based on other parameters.
         CreateInfo(const SkImageInfo& info,
                    TileUsage tileUsage,
-                   SkPixelGeometry geo,
+                   SkPixelGeometry geo)
-                   bool forImageFilter = false)
             : fInfo(info)
             , fTileUsage(tileUsage)
-            , fPixelGeometry(AdjustGeometry(info, tileUsage, geo))
+            , fPixelGeometry(AdjustGeometry(info, tileUsage, geo, false))
+            , fForImageFilter(false) {}
+
+        CreateInfo(const SkImageInfo& info,
+                   TileUsage tileUsage,
+                   SkPixelGeometry geo,
+                   bool preserveLCDText,
+                   bool forImageFilter)
+            : fInfo(info)
+            , fTileUsage(tileUsage)
+            , fPixelGeometry(AdjustGeometry(info, tileUsage, geo, preserveLCDText))
             , fForImageFilter(forImageFilter) {}
 
         const SkImageInfo       fInfo;

src/core/SkCanvas.cpp

@@ -1140,6 +1140,12 @@ int SkCanvas::saveLayer(const SkRect* bounds, const SkPaint* paint, SaveFlags fl
     return this->getSaveCount() - 1;
 }
 
+int SkCanvas::saveLayerPreserveLCDTextRequests(const SkRect* bounds, const SkPaint* paint) {
+    unsigned flags = kARGB_ClipLayer_SaveFlag | kPreserveLCDText_PrivateSaveFlag;
+    return this->saveLayer(bounds, paint, (SaveFlags)flags);
+}
+
+
 void SkCanvas::internalSaveLayer(const SkRect* bounds, const SkPaint* paint, SaveFlags flags,
                                  SaveLayerStrategy strategy) {
 #ifndef SK_SUPPORT_LEGACY_CLIPTOLAYERFLAG
@@ -1183,8 +1189,11 @@ void SkCanvas::internalSaveLayer(const SkRect* bounds, const SkPaint* paint, Sav
 
     bool forceSpriteOnRestore = false;
     {
+        const bool preserveLCDText = kOpaque_SkAlphaType == info.alphaType() ||
+                                     SkToBool(flags & kPreserveLCDText_PrivateSaveFlag);
         const SkBaseDevice::TileUsage usage = SkBaseDevice::kNever_TileUsage;
-        const SkBaseDevice::CreateInfo createInfo = SkBaseDevice::CreateInfo(info, usage, geo);
+        const SkBaseDevice::CreateInfo createInfo = SkBaseDevice::CreateInfo(info, usage, geo,
+                                                                            preserveLCDText, false);
         SkBaseDevice* newDev = device->onCreateDevice(createInfo, paint);
         if (nullptr == newDev) {
             // If onCreateDevice didn't succeed, try raster (e.g. PDF couldn't handle the paint)

src/core/SkDevice.cpp

@@ -55,7 +55,8 @@ const SkBitmap& SkBaseDevice::accessBitmap(bool changePixels) {
 
 SkPixelGeometry SkBaseDevice::CreateInfo::AdjustGeometry(const SkImageInfo& info,
                                                          TileUsage tileUsage,
-                                                         SkPixelGeometry geo) {
+                                                         SkPixelGeometry geo,
+                                                         bool preserveLCDText) {
     switch (tileUsage) {
         case kPossible_TileUsage:
             // (we think) for compatibility with old clients, we assume this layer can support LCD
@@ -63,7 +64,7 @@ SkPixelGeometry SkBaseDevice::CreateInfo::AdjustGeometry(const SkImageInfo& info
             // our callers (reed/robertphilips).
             break;
         case kNever_TileUsage:
-            if (info.alphaType() != kOpaque_SkAlphaType) {
+            if (!preserveLCDText) {
                 geo = kUnknown_SkPixelGeometry;
             }
             break;

src/core/SkImageFilter.cpp

@@ -658,6 +658,7 @@ SkBaseDevice* SkImageFilter::DeviceProxy::createDevice(int w, int h) {
     SkBaseDevice::CreateInfo cinfo(SkImageInfo::MakeN32Premul(w, h),
                                    SkBaseDevice::kNever_TileUsage,
                                    kUnknown_SkPixelGeometry,
+                                   false,   /* preserveLCDText */
                                    true /*forImageFilter*/);
     SkBaseDevice* dev = fDevice->onCreateDevice(cinfo, nullptr);
     if (nullptr == dev) {