Simplify some Viewer code, and fix a few bugs

The content rect was always identical to the window rect,
so most of the related code did nothing. The translation
limit code is always useful (to avoid dragging the slide
way off-screen with the mouse), so always include it.
The auto-scaling to fit the screen is also still useful,
but just base it on the window rect.

The zoom code has four state variables, only used two of
them, and one was a trivially derived computation. Fold
most of that work into computeMatrix. (The translation
was always zero -- we never changed the zoom center.)

Include fDefaultMatrix in the matrix from computeMatrix,
rather than needing to apply it specially to the canvas.

Don't apply the inverse default matrix to touch or mouse
points. The absolute positions of those touch points is
not important, but because that matrix includes scale
(and sometimes very large or very small scale), it just
had the effect of greatly amplifying or damping the drag
speed. Without it, the slide always pans at the speed of
the touch/mouse drag -- which seems more desirable.

The use of the inverse default matrix was a clever trick,
but it caused the translation (applied to the global mtx)
to be scaled, so the slide was always pinned incorrectly.
Instead, supply the unmodified window rect and the default
matrix, so the trans limit code can do the obvious correct
thing: xform the slide bounds completely, then limit the
translation that will be applied after that. Slides are
now correctly pinned to screen edge regardless of how
much zoom is present in the default matrix.

Note: There are still several bugs related to all of this
code, but given the web of xform state, it's hard to
unravel. The touch gesture still doesn't know about
viewer's zoom, so that's ignored when doing the pinning.
Beyond that, it doesn't even know about window resize -
it only configures the translation limit when setting up
a slide. I had a fix for all of this (doing the
translation limiting in computeMatrix), but then the touch
gesture doesn't know about it, and can accumulate drag
motion that needs to be un-dragged to get back on-screen,
even though the slide is never really translated that far.

SkTouchGesture is in include. No one uses it except viewer:
TBR=bsalomon@google.com

Bug: skia:
Change-Id: I460cc07c3de6d36e63826f57d359faf1facf5ab3
Reviewed-on: https://skia-review.googlesource.com/18524
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: Yuqian Li <liyuqian@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

7 files changed, 28 insertions, 77 deletions

diff --git a/include/views/SkTouchGesture.h b/include/views/SkTouchGesture.h
index 4d4c0312d3..6776de7267 100644
--- a/include/views/SkTouchGesture.h
+++ b/include/views/SkTouchGesture.h
@@ -43,7 +43,8 @@ public:
     const SkMatrix& localM();
     const SkMatrix& globalM() const { return fGlobalM; }
 
-    void setTransLimit(const SkRect& contentRect, const SkRect& windowRect);
+    void setTransLimit(const SkRect& contentRect, const SkRect& windowRect,
+                       const SkMatrix& preTouchM);
 
 private:
     enum State {
@@ -62,7 +63,7 @@ private:
     SkTDArray<Rec> fTouches;
 
     State           fState;
-    SkMatrix        fLocalM, fGlobalM;
+    SkMatrix        fLocalM, fGlobalM, fPreTouchM;
     SkFlingState    fFlinger;
     double          fLastUpMillis;
     SkPoint         fLastUpP;
diff --git a/src/views/SkTouchGesture.cpp b/src/views/SkTouchGesture.cpp
index 752828e37f..cd7388b6e1 100644
--- a/src/views/SkTouchGesture.cpp
+++ b/src/views/SkTouchGesture.cpp
@@ -331,10 +331,12 @@ bool SkTouchGesture::handleDblTap(float x, float y) {
     return found;
 }
 
-void SkTouchGesture::setTransLimit(const SkRect& contentRect, const SkRect& windowRect) {
+void SkTouchGesture::setTransLimit(const SkRect& contentRect, const SkRect& windowRect,
+                                   const SkMatrix& preTouchMatrix) {
     fIsTransLimited = true;
     fContentRect = contentRect;
     fWindowRect = windowRect;
+    fPreTouchM = preTouchMatrix;
 }
 
 void SkTouchGesture::limitTrans() {
@@ -343,6 +345,7 @@ void SkTouchGesture::limitTrans() {
     }
 
     SkRect scaledContent = fContentRect;
+    fPreTouchM.mapRect(&scaledContent);
     fGlobalM.mapRect(&scaledContent);
     const SkScalar ZERO = 0;
 
diff --git a/tools/viewer/Viewer.cpp b/tools/viewer/Viewer.cpp
index d1e48dda09..3503e6481f 100644
--- a/tools/viewer/Viewer.cpp
+++ b/tools/viewer/Viewer.cpp
@@ -250,10 +250,7 @@ Viewer::Viewer(int argc, char** argv, void* platformData)
     , fBackendType(sk_app::Window::kNativeGL_BackendType)
     , fColorMode(ColorMode::kLegacy)
     , fColorSpacePrimaries(gSrgbPrimaries)
-    , fZoomCenterX(0.0f)
-    , fZoomCenterY(0.0f)
     , fZoomLevel(0.0f)
-    , fZoomScale(SK_Scalar1)
 {
     static SkTaskGroup::Enabler kTaskGroupEnabler;
     SkGraphics::Init();
@@ -619,26 +616,20 @@ void Viewer::setupCurrentSlide(int previousSlide) {
 
     fGesture.reset();
     fDefaultMatrix.reset();
-    fDefaultMatrixInv.reset();
-
-    if (fWindow->supportsContentRect() && fWindow->scaleContentToFit()) {
-        const SkRect contentRect = fWindow->getContentRect();
-        const SkISize slideSize = fSlides[fCurrentSlide]->getDimensions();
-        const SkRect slideBounds = SkRect::MakeIWH(slideSize.width(), slideSize.height());
-        if (contentRect.width() > 0 && contentRect.height() > 0) {
-            fDefaultMatrix.setRectToRect(slideBounds, contentRect, SkMatrix::kStart_ScaleToFit);
-            SkAssertResult(fDefaultMatrix.invert(&fDefaultMatrixInv));
+
+    const SkISize slideSize = fSlides[fCurrentSlide]->getDimensions();
+    const SkRect slideBounds = SkRect::MakeIWH(slideSize.width(), slideSize.height());
+    const SkRect windowRect = SkRect::MakeIWH(fWindow->width(), fWindow->height());
+
+    // Start with a matrix that scales the slide to the available screen space
+    if (fWindow->scaleContentToFit()) {
+        if (windowRect.width() > 0 && windowRect.height() > 0) {
+            fDefaultMatrix.setRectToRect(slideBounds, windowRect, SkMatrix::kStart_ScaleToFit);
         }
     }
 
-    if (fWindow->supportsContentRect()) {
-        const SkISize slideSize = fSlides[fCurrentSlide]->getDimensions();
-        SkRect windowRect = fWindow->getContentRect();
-        fDefaultMatrixInv.mapRect(&windowRect);
-        fGesture.setTransLimit(SkRect::MakeWH(SkIntToScalar(slideSize.width()), 
-                                              SkIntToScalar(slideSize.height())),
-                               windowRect);
-    }
+    // Prevent the user from dragging content so far outside the window they can't find it again
+    fGesture.setTransLimit(slideBounds, windowRect, fDefaultMatrix);
 
     this->updateTitle();
     this->updateUIState();
@@ -653,35 +644,18 @@ void Viewer::setupCurrentSlide(int previousSlide) {
 
 void Viewer::changeZoomLevel(float delta) {
     fZoomLevel += delta;
-    if (fZoomLevel > 0) {
-        fZoomLevel = SkMinScalar(fZoomLevel, MAX_ZOOM_LEVEL);
-        fZoomScale = fZoomLevel + SK_Scalar1;
-    } else if (fZoomLevel < 0) {
-        fZoomLevel = SkMaxScalar(fZoomLevel, MIN_ZOOM_LEVEL);
-        fZoomScale = SK_Scalar1 / (SK_Scalar1 - fZoomLevel);
-    } else {
-        fZoomScale = SK_Scalar1;
-    }
+    fZoomLevel = SkScalarPin(fZoomLevel, MIN_ZOOM_LEVEL, MAX_ZOOM_LEVEL);
 }
 
 SkMatrix Viewer::computeMatrix() {
     SkMatrix m;
-    m.reset();
-
-    if (fZoomLevel) {
-        SkPoint center;
-        //m = this->getLocalMatrix();//.invert(&m);
-        m.mapXY(fZoomCenterX, fZoomCenterY, &center);
-        SkScalar cx = center.fX;
-        SkScalar cy = center.fY;
-
-        m.setTranslate(-cx, -cy);
-        m.postScale(fZoomScale, fZoomScale);
-        m.postTranslate(cx, cy);
-    }
 
-    m.preConcat(fGesture.localM());
+    SkScalar zoomScale = (fZoomLevel < 0) ? SK_Scalar1 / (SK_Scalar1 - fZoomLevel)
+                                          : SK_Scalar1 + fZoomLevel;
+    m = fGesture.localM();
     m.preConcat(fGesture.globalM());
+    m.preConcat(fDefaultMatrix);
+    m.preScale(zoomScale, zoomScale);
 
     return m;
 }
@@ -737,12 +711,6 @@ void Viewer::setColorMode(ColorMode colorMode) {
 void Viewer::drawSlide(SkCanvas* canvas) {
     SkAutoCanvasRestore autorestore(canvas, false);
 
-    if (fWindow->supportsContentRect()) {
-        SkRect contentRect = fWindow->getContentRect();
-        canvas->clipRect(contentRect);
-        canvas->translate(contentRect.fLeft, contentRect.fTop);
-    }
-
     // By default, we render directly into the window's surface/canvas
     SkCanvas* slideCanvas = canvas;
     fLastImage.reset();
@@ -785,7 +753,6 @@ void Viewer::drawSlide(SkCanvas* canvas) {
 
     int count = slideCanvas->save();
     slideCanvas->clear(SK_ColorWHITE);
-    slideCanvas->concat(fDefaultMatrix);
     slideCanvas->concat(computeMatrix());
     // Time the painting logic of the slide
     double startTime = SkTime::GetMSecs();
@@ -853,18 +820,17 @@ void Viewer::onPaint(SkCanvas* canvas) {
 
 bool Viewer::onTouch(intptr_t owner, Window::InputState state, float x, float y) {
     void* castedOwner = reinterpret_cast<void*>(owner);
-    SkPoint touchPoint = fDefaultMatrixInv.mapXY(x, y);
     switch (state) {
         case Window::kUp_InputState: {
             fGesture.touchEnd(castedOwner);
             break;
         }
         case Window::kDown_InputState: {
-            fGesture.touchBegin(castedOwner, touchPoint.fX, touchPoint.fY);
+            fGesture.touchBegin(castedOwner, x, y);
             break;
         }
         case Window::kMove_InputState: {
-            fGesture.touchMoved(castedOwner, touchPoint.fX, touchPoint.fY);
+            fGesture.touchMoved(castedOwner, x, y);
             break;
         }
     }
@@ -873,19 +839,17 @@ bool Viewer::onTouch(intptr_t owner, Window::InputState state, float x, float y)
 }
 
 bool Viewer::onMouse(float x, float y, Window::InputState state, uint32_t modifiers) {
-
-    SkPoint touchPoint = fDefaultMatrixInv.mapXY(x, y);
     switch (state) {
         case Window::kUp_InputState: {
             fGesture.touchEnd(nullptr);
             break;
         }
         case Window::kDown_InputState: {
-            fGesture.touchBegin(nullptr, touchPoint.fX, touchPoint.fY);
+            fGesture.touchBegin(nullptr, x, y);
             break;
         }
         case Window::kMove_InputState: {
-            fGesture.touchMoved(nullptr, touchPoint.fX, touchPoint.fY);
+            fGesture.touchMoved(nullptr, x, y);
             break;
         }
     }
@@ -908,12 +872,6 @@ void Viewer::drawStats(SkCanvas* canvas) {
     SkPaint paint;
     canvas->save();
 
-    if (fWindow->supportsContentRect()) {
-        SkRect contentRect = fWindow->getContentRect();
-        canvas->clipRect(contentRect);
-        canvas->translate(contentRect.fLeft, contentRect.fTop);
-    }
-
     canvas->clipRect(rect);
     paint.setColor(SK_ColorBLACK);
     canvas->drawRect(rect, paint);
diff --git a/tools/viewer/Viewer.h b/tools/viewer/Viewer.h
index 09a8946ac9..fac280ff59 100644
--- a/tools/viewer/Viewer.h
+++ b/tools/viewer/Viewer.h
@@ -87,10 +87,7 @@ private:
     SkColorSpacePrimaries  fColorSpacePrimaries;
 
     // transform data
-    SkScalar               fZoomCenterX;
-    SkScalar               fZoomCenterY;
     SkScalar               fZoomLevel;
-    SkScalar               fZoomScale;
 
     sk_app::CommandSet     fCommands;
 
@@ -98,7 +95,6 @@ private:
 
     // identity unless the window initially scales the content to fit the screen.
     SkMatrix               fDefaultMatrix;
-    SkMatrix               fDefaultMatrixInv;
 
     SkTArray<std::function<void(void)>> fDeferredActions;
 
diff --git a/tools/viewer/sk_app/Window.h b/tools/viewer/sk_app/Window.h
index c5d8c346af..752dc47548 100644
--- a/tools/viewer/sk_app/Window.h
+++ b/tools/viewer/sk_app/Window.h
@@ -38,8 +38,6 @@ public:
     void inval();
 
     virtual bool scaleContentToFit() const { return false; }
-    virtual bool supportsContentRect() const { return false; }
-    virtual SkRect getContentRect() { return SkRect::MakeEmpty(); }
 
     enum BackendType {
         kNativeGL_BackendType,
diff --git a/tools/viewer/sk_app/android/Window_android.h b/tools/viewer/sk_app/android/Window_android.h
index 062f2fec2d..791801140e 100644
--- a/tools/viewer/sk_app/android/Window_android.h
+++ b/tools/viewer/sk_app/android/Window_android.h
@@ -32,13 +32,9 @@ public:
     void paintIfNeeded();
 
     bool scaleContentToFit() const override { return true; }
-    bool supportsContentRect() const override { return true; }
-    SkRect getContentRect() override { return fContentRect; }
-    void setContentRect(int l, int t, int r, int b) { fContentRect.set(l,t,r,b); }
 
 private:
     SkiaAndroidApp* fSkiaAndroidApp = nullptr;
-    SkRect fContentRect;
     BackendType fBackendType;
 };
 
diff --git a/tools/viewer/sk_app/android/surface_glue_android.cpp b/tools/viewer/sk_app/android/surface_glue_android.cpp
index 178f04d074..4fb6c3d9ac 100644
--- a/tools/viewer/sk_app/android/surface_glue_android.cpp
+++ b/tools/viewer/sk_app/android/surface_glue_android.cpp
@@ -123,7 +123,6 @@ int SkiaAndroidApp::message_callback(int fd, int events, void* data) {
                 window_android->initDisplay(skiaAndroidApp->fNativeWindow);
             }
             window_android->onResize(width, height);
-            window_android->setContentRect(0, 0, width, height);
             window_android->paintIfNeeded();
             break;
         }