Transform vertices for distance field glyphs on CPU.

This allows batching of DF draws with different view matrices.

For perspective matrices this means the transformed position vertex
attribute must have w values. Currently, non-perspective DF draws still
use 2 component positions, though this could be changed in the future.
Consequently, perspective draws can batch with other perspective draws
but not non-perspective draws.

Adds a GM to test batching and reusing the same blobs with both perspective
and non-perspective matrices.

Change-Id: I0e42c5449ebf3a5a54025dbcdec824d904d5bd9e
Reviewed-on: https://skia-review.googlesource.com/79900
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>

1 files changed, 143 insertions, 0 deletions

diff --git a/gm/dftext_blob_persp.cpp b/gm/dftext_blob_persp.cpp
new file mode 100644
index 0000000000..cfa681d984
--- /dev/null
+++ b/gm/dftext_blob_persp.cpp
@@ -0,0 +1,143 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "gm.h"
+#include "Resources.h"
+#include "SkCanvas.h"
+#include "SkSurface.h"
+#include "SkTextBlob.h"
+#include "SkTypeface.h"
+#include "sk_tool_utils.h"
+
+/**
+ * This GM tests reusing the same text blobs with distance fields rendering using various
+ * combinations of perspective and non-perspetive matrices, scissor clips, and different x,y params
+ * passed to the draw.
+ */
+class DFTextBlobPerspGM : public skiagm::GM {
+public:
+    DFTextBlobPerspGM() { this->setBGColor(0xFFFFFFFF); }
+
+protected:
+    SkString onShortName() override {
+        SkString name("dftext_blob_persp");
+        name.append(sk_tool_utils::platform_font_manager());
+        return name;
+    }
+
+    SkISize onISize() override { return SkISize::Make(900, 350); }
+
+    void onOnceBeforeDraw() override {
+        for (int i = 0; i < 3; ++i) {
+            SkPaint paint;
+            paint.setTextSize(32);
+            paint.setAntiAlias(i > 0);
+            paint.setLCDRenderText(i > 1);
+            paint.setSubpixelText(true);
+            SkTextBlobBuilder builder;
+            sk_tool_utils::add_to_text_blob(&builder, "SkiaText", paint, 0, 0);
+            fBlobs.emplace_back(builder.make());
+        }
+    }
+
+    virtual void onDraw(SkCanvas* inputCanvas) override {
+    // set up offscreen rendering with distance field text
+#if SK_SUPPORT_GPU
+        GrContext* ctx = inputCanvas->getGrContext();
+        SkISize size = this->onISize();
+        if (!inputCanvas->getBaseLayerSize().isEmpty()) {
+            size = inputCanvas->getBaseLayerSize();
+        }
+        SkImageInfo info = SkImageInfo::MakeN32(size.width(), size.height(), kPremul_SkAlphaType,
+                                                inputCanvas->imageInfo().refColorSpace());
+        SkSurfaceProps props(SkSurfaceProps::kUseDeviceIndependentFonts_Flag,
+                             SkSurfaceProps::kLegacyFontHost_InitType);
+        auto surface = SkSurface::MakeRenderTarget(ctx, SkBudgeted::kNo, info, 0, &props);
+        SkCanvas* canvas = surface ? surface->getCanvas() : inputCanvas;
+        // init our new canvas with the old canvas's matrix
+        canvas->setMatrix(inputCanvas->getTotalMatrix());
+#else
+        SkCanvas* canvas = inputCanvas;
+#endif
+        SkScalar x = 0, y = 0;
+        SkScalar maxH = 0;
+        for (auto twm : {TranslateWithMatrix::kNo, TranslateWithMatrix::kYes}) {
+            for (auto pm : {PerspMode::kNone, PerspMode::kX, PerspMode::kY, PerspMode::kXY}) {
+                for (auto& blob : fBlobs) {
+                    for (bool clip : {false, true}) {
+                        canvas->save();
+                        SkScalar w = blob->bounds().width();
+                        SkScalar h = blob->bounds().height();
+                        if (clip) {
+                            auto rect =
+                                    SkRect::MakeXYWH(x + 5, y + 5, w * 3.f / 4.f, h * 3.f / 4.f);
+                            canvas->clipRect(rect, false);
+                        }
+                        this->drawBlob(canvas, blob.get(), SK_ColorBLACK, x, y + h, pm, twm);
+                        x += w + 20.f;
+                        maxH = SkTMax(h, maxH);
+                        canvas->restore();
+                    }
+                }
+                x = 0;
+                y += maxH + 20.f;
+                maxH = 0;
+            }
+        }
+#if SK_SUPPORT_GPU
+        // render offscreen buffer
+        if (surface) {
+            SkAutoCanvasRestore acr(inputCanvas, true);
+            // since we prepended this matrix already, we blit using identity
+            inputCanvas->resetMatrix();
+            inputCanvas->drawImage(surface->makeImageSnapshot().get(), 0, 0, nullptr);
+        }
+#endif
+    }
+
+private:
+    enum class PerspMode { kNone, kX, kY, kXY };
+
+    enum class TranslateWithMatrix : bool { kNo, kYes };
+
+    void drawBlob(SkCanvas* canvas, SkTextBlob* blob, SkColor color, SkScalar x, SkScalar y,
+                  PerspMode perspMode, TranslateWithMatrix translateWithMatrix) {
+        canvas->save();
+        SkMatrix persp = SkMatrix::I();
+        switch (perspMode) {
+            case PerspMode::kNone:
+                break;
+            case PerspMode::kX:
+                persp.setPerspX(0.005f);
+                break;
+            case PerspMode::kY:
+                persp.setPerspY(00.005f);
+                break;
+            case PerspMode::kXY:
+                persp.setPerspX(-0.001f);
+                persp.setPerspY(-0.0015f);
+                break;
+        }
+        persp = SkMatrix::Concat(persp, SkMatrix::MakeTrans(-x, -y));
+        persp = SkMatrix::Concat(SkMatrix::MakeTrans(x, y), persp);
+        canvas->concat(persp);
+        if (TranslateWithMatrix::kYes == translateWithMatrix) {
+            canvas->translate(x, y);
+            x = 0;
+            y = 0;
+        }
+        SkPaint paint;
+        paint.setColor(color);
+        canvas->drawTextBlob(blob, x, y, paint);
+        canvas->restore();
+    }
+
+    SkTArray<sk_sp<SkTextBlob>, true> fBlobs;
+    typedef skiagm::GM INHERITED;
+};
+
+DEF_GM(return new DFTextBlobPerspGM;)