Resurrect pathfinder in viewer and rename to "bisect"

Bug: skia:
Change-Id: If8d2f46b8f27fefc3a0f983eb649654e0fb4afcb
Reviewed-on: https://skia-review.googlesource.com/108685
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
diff --git a/tools/viewer/BisectSlide.cpp b/tools/viewer/BisectSlide.cpp
new file mode 100644
index 0000000..63e69d2
--- /dev/null
+++ b/tools/viewer/BisectSlide.cpp
@@ -0,0 +1,130 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "BisectSlide.h"
+
+#include "SkDOM.h"
+#include "SkOSPath.h"
+#include "SkPicture.h"
+#include "SkStream.h"
+#include "../experimental/svg/model/SkSVGDOM.h"
+
+sk_sp<BisectSlide> BisectSlide::Create(const char filepath[]) {
+    SkFILEStream stream(filepath);
+    if (!stream.isValid()) {
+        SkDebugf("BISECT: invalid input file at \"%s\"\n", filepath);
+        return nullptr;
+    }
+
+    sk_sp<BisectSlide> bisect(new BisectSlide(filepath));
+    if (bisect->fFilePath.endsWith(".svg")) {
+        SkDOM xml;
+        if (!xml.build(stream)) {
+            SkDebugf("BISECT: XML parsing failed: \"%s\"\n", filepath);
+            return nullptr;
+        }
+        sk_sp<SkSVGDOM> svg = SkSVGDOM::MakeFromDOM(xml);
+        if (!svg) {
+            SkDebugf("BISECT: couldn't load svg at \"%s\"\n", filepath);
+            return nullptr;
+        }
+        svg->setContainerSize(SkSize::Make(bisect->getDimensions()));
+        svg->render(bisect.get());
+    } else {
+        sk_sp<SkPicture> skp = SkPicture::MakeFromStream(&stream);
+        if (!skp) {
+            SkDebugf("BISECT: couldn't load skp at \"%s\"\n", filepath);
+            return nullptr;
+        }
+        skp->playback(bisect.get());
+    }
+
+    return bisect;
+}
+
+BisectSlide::BisectSlide(const char filepath[])
+        : SkCanvas(4096, 4096, nullptr)
+        , fFilePath(filepath) {
+    const char* basename = strrchr(fFilePath.c_str(), SkOSPath::SEPARATOR);
+    fName.printf("BISECT_%s", basename ? basename + 1 : fFilePath.c_str());
+}
+
+// Called through SkPicture::playback only during creation.
+void BisectSlide::onDrawPath(const SkPath& path, const SkPaint& paint) {
+    SkRect bounds;
+    SkIRect ibounds;
+    this->getTotalMatrix().mapRect(&bounds, path.getBounds());
+    bounds.roundOut(&ibounds);
+    fDrawBounds.join(ibounds);
+    fFoundPaths.push_back() = {path, paint, this->getTotalMatrix()};
+}
+
+bool BisectSlide::onChar(SkUnichar c) {
+    switch (c) {
+        case 'X':
+            if (!fTossedPaths.empty()) {
+                SkTSwap(fFoundPaths, fTossedPaths);
+                if ('X' == fTrail.back()) {
+                    fTrail.pop_back();
+                } else {
+                    fTrail.push_back('X');
+                }
+            }
+            return true;
+
+        case 'x':
+            if (fFoundPaths.count() > 1) {
+                int midpt = (fFoundPaths.count() + 1) / 2;
+                fPathHistory.emplace(fFoundPaths, fTossedPaths);
+                fTossedPaths.reset(fFoundPaths.begin() + midpt, fFoundPaths.count() - midpt);
+                fFoundPaths.resize_back(midpt);
+                fTrail.push_back('x');
+            }
+            return true;
+
+        case 'Z': {
+            if (!fPathHistory.empty()) {
+                fFoundPaths = fPathHistory.top().first;
+                fTossedPaths = fPathHistory.top().second;
+                fPathHistory.pop();
+                char ch;
+                do {
+                    ch = fTrail.back();
+                    fTrail.pop_back();
+                } while (ch != 'x');
+            }
+            return true;
+        }
+
+        case 'D':
+            SkDebugf("viewer --bisect %s", fFilePath.c_str());
+            if (!fTrail.empty()) {
+                SkDebugf(" ");
+                for (char ch : fTrail) {
+                    SkDebugf("%c", ch);
+                }
+            }
+            SkDebugf("\n");
+            for (const FoundPath& foundPath : fFoundPaths) {
+                foundPath.fPath.dump();
+            }
+            return true;
+    }
+
+    return false;
+}
+
+void BisectSlide::draw(SkCanvas* canvas) {
+    SkAutoCanvasRestore acr(canvas, true);
+    canvas->translate(-fDrawBounds.left(), -fDrawBounds.top());
+
+    for (const FoundPath& path : fFoundPaths) {
+        SkAutoCanvasRestore acr(canvas, true);
+        canvas->concat(path.fViewMatrix);
+        canvas->drawPath(path.fPath, path.fPaint);
+    }
+}
diff --git a/tools/viewer/BisectSlide.h b/tools/viewer/BisectSlide.h
new file mode 100644
index 0000000..c5300c6
--- /dev/null
+++ b/tools/viewer/BisectSlide.h
@@ -0,0 +1,54 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef BisectSlide_DEFINED
+#define BisectSlide_DEFINED
+
+#include "SkCanvas.h"
+#include "SkPath.h"
+#include "Slide.h"
+#include <stack>
+
+/**
+ * This is a simple utility designed to extract the paths from an SKP file and then isolate a single
+ * one of them via bisect. Use the 'x' and 'X' keys to guide a binary search:
+ *
+ *   'x': Throw out half the paths.
+ *   'X': Toggle which half gets tossed and which half is kept.
+ *   'Z': Back up one level.
+ *   'D': Dump the path.
+ */
+class BisectSlide : public Slide, public SkCanvas {
+public:
+    static sk_sp<BisectSlide> Create(const char filepath[]);
+
+    // Slide overrides.
+    SkISize getDimensions() const override { return fDrawBounds.size(); }
+    bool onChar(SkUnichar c) override;
+    void draw(SkCanvas* canvas) override;
+
+private:
+    BisectSlide(const char filepath[]);
+
+    // SkCanvas override called only during creation.
+    void onDrawPath(const SkPath& path, const SkPaint& paint) override;
+
+    struct FoundPath {
+        SkPath fPath;
+        SkPaint fPaint;
+        SkMatrix fViewMatrix;
+    };
+
+    SkString fFilePath;
+    SkIRect fDrawBounds = SkIRect::MakeEmpty();
+    SkTArray<FoundPath> fFoundPaths;
+    SkTArray<FoundPath> fTossedPaths;
+    SkTArray<char> fTrail;
+    std::stack<std::pair<SkTArray<FoundPath>, SkTArray<FoundPath>>> fPathHistory;
+};
+
+#endif
diff --git a/tools/viewer/Viewer.cpp b/tools/viewer/Viewer.cpp
index c412218..6582490 100644
--- a/tools/viewer/Viewer.cpp
+++ b/tools/viewer/Viewer.cpp
@@ -7,6 +7,7 @@
 
 #include "Viewer.h"
 
+#include "BisectSlide.h"
 #include "GMSlide.h"
 #include "ImageSlide.h"
 #include "Resources.h"
@@ -82,6 +83,8 @@
 
 static DEFINE_int32(msaa, 1, "Number of subpixel samples. 0 for no HW antialiasing.");
 
+DEFINE_string(bisect, "", "Path to a .skp or .svg file to bisect.");
+
 DECLARE_int32(threads)
 
 const char* kBackendTypeStrings[sk_app::Window::kBackendTypeCount] = {
@@ -478,23 +481,36 @@
 void Viewer::initSlides() {
     fAllSlideNames = Json::Value(Json::arrayValue);
 
+    // Bisect slide.
+    if (!FLAGS_bisect.isEmpty()) {
+        sk_sp<BisectSlide> bisect = BisectSlide::Create(FLAGS_bisect[0]);
+        if (bisect && !SkCommandLineFlags::ShouldSkip(FLAGS_match, bisect->getName().c_str())) {
+            if (FLAGS_bisect.count() >= 2) {
+                for (const char* ch = FLAGS_bisect[1]; *ch; ++ch) {
+                    bisect->onChar(*ch);
+                }
+            }
+            fSlides.push_back(std::move(bisect));
+        }
+    }
+
+    // GMs
+    int firstGM = fSlides.count();
     const skiagm::GMRegistry* gms(skiagm::GMRegistry::Head());
     while (gms) {
         std::unique_ptr<skiagm::GM> gm(gms->factory()(nullptr));
 
         if (!SkCommandLineFlags::ShouldSkip(FLAGS_match, gm->getName())) {
             sk_sp<Slide> slide(new GMSlide(gm.release()));
-            fSlides.push_back(slide);
+            fSlides.push_back(std::move(slide));
         }
 
         gms = gms->next();
     }
-
-    // reverse array
-    for (int i = 0; i < fSlides.count()/2; ++i) {
-        sk_sp<Slide> temp = fSlides[i];
-        fSlides[i] = fSlides[fSlides.count() - i - 1];
-        fSlides[fSlides.count() - i - 1] = temp;
+    // reverse gms
+    int numGMs = fSlides.count() - firstGM;
+    for (int i = 0; i < numGMs/2; ++i) {
+        std::swap(fSlides[firstGM + i], fSlides[fSlides.count() - i - 1]);
     }
 
     // samples