Force tiles in SampleApp to integer boundaries.

The current behavior is to create tiles from the rounded ideal tile size,
tell the tile that it's upper left pixel is at the ideal location, and
then draw those tiles at the ideal locations. As a result, the tiles are
be out of phase with each other internally and then actually drawn at
the rounded pixel location instead of the ideal location.

The new behavior is to always round up to get the tile size, make the
tile translation an integer offset, and then draw at the exact pixel.

This also modifies SampleApp to use the numeric keypad to provide an
extra manual 1/32 pixel translation for fine grained movement.

BUG=skia:5020

Review URL: https://codereview.chromium.org/1763833002

1 files changed, 39 insertions, 13 deletions

diff --git a/samplecode/SampleApp.cpp b/samplecode/SampleApp.cpp
index 7ebac5f215..6d5f647b15 100644
--- a/samplecode/SampleApp.cpp
+++ b/samplecode/SampleApp.cpp
@@ -876,7 +876,6 @@ SampleWindow::SampleWindow(void* hwnd, int argc, char** argv, DeviceManager* dev
     fHintingState = 0;
     fFilterQualityIndex = 0;
     fFlipAxis = 0;
-    fScrollTestX = fScrollTestY = 0;
 
     fMouseX = fMouseY = 0;
     fFatBitsScale = 8;
@@ -885,6 +884,7 @@ SampleWindow::SampleWindow(void* hwnd, int argc, char** argv, DeviceManager* dev
 
     fZoomLevel = 0;
     fZoomScale = SK_Scalar1;
+    fOffset = { 0, 0 };
 
     fMagnify = false;
 
@@ -1062,14 +1062,14 @@ void SampleWindow::draw(SkCanvas* canvas) {
     if (kNo_Tiling == fTilingMode) {
         this->INHERITED::draw(canvas); // no looping or surfaces needed
     } else {
-        const int w = SkScalarRoundToInt(tile.width());
-        const int h = SkScalarRoundToInt(tile.height());
-        SkImageInfo info = SkImageInfo::MakeN32Premul(w, h);
+        const SkScalar w = SkScalarCeilToScalar(tile.width());
+        const SkScalar h = SkScalarCeilToScalar(tile.height());
+        SkImageInfo info = SkImageInfo::MakeN32Premul(SkScalarTruncToInt(w), SkScalarTruncToInt(h));
         SkAutoTUnref<SkSurface> surface(canvas->newSurface(info));
         SkCanvas* tileCanvas = surface->getCanvas();
 
-        for (SkScalar y = 0; y < height(); y += tile.height()) {
-            for (SkScalar x = 0; x < width(); x += tile.width()) {
+        for (SkScalar y = 0; y < height(); y += h) {
+            for (SkScalar x = 0; x < width(); x += w) {
                 SkAutoCanvasRestore acr(tileCanvas, true);
                 tileCanvas->translate(-x, -y);
                 tileCanvas->clear(0);
@@ -1462,6 +1462,11 @@ void SampleWindow::beforeChild(SkView* child, SkCanvas* canvas) {
     }
 }
 
+void SampleWindow::changeOffset(SkVector delta) {
+    fOffset += delta;
+    this->updateMatrix();
+}
+
 void SampleWindow::changeZoomLevel(float delta) {
     fZoomLevel += delta;
     if (fZoomLevel > 0) {
@@ -1479,6 +1484,7 @@ void SampleWindow::changeZoomLevel(float delta) {
 void SampleWindow::updateMatrix(){
     SkMatrix m;
     m.reset();
+
     if (fZoomLevel) {
         SkPoint center;
         //m = this->getLocalMatrix();//.invert(&m);
@@ -1491,6 +1497,8 @@ void SampleWindow::updateMatrix(){
         m.postTranslate(cx, cy);
     }
 
+    m.postTranslate(fOffset.fX, fOffset.fY);
+
     if (fFlipAxis) {
         m.preTranslate(fZoomCenterX, fZoomCenterY);
         if (fFlipAxis & kFlipAxis_X) {
@@ -1685,13 +1693,7 @@ bool SampleWindow::onHandleChar(SkUnichar uni) {
     }
 
     if (0xFF != dx && 0xFF != dy) {
-        if ((dx | dy) == 0) {
-            fScrollTestX = fScrollTestY = 0;
-        } else {
-            fScrollTestX += dx;
-            fScrollTestY += dy;
-        }
-        this->inval(nullptr);
+        this->changeOffset({SkIntToScalar(dx / 32.0f), SkIntToScalar(dy / 32.0f)});
         return true;
     }
 
@@ -1855,6 +1857,10 @@ bool SampleWindow::onHandleKey(SkKey key) {
             }
         }
     }
+
+    int dx = 0xFF;
+    int dy = 0xFF;
+
     switch (key) {
         case kRight_SkKey:
             if (this->nextSample()) {
@@ -1882,9 +1888,26 @@ bool SampleWindow::onHandleKey(SkKey key) {
         case kBack_SkKey:
             this->showOverview();
             return true;
+
+        case k5_SkKey: dx =  0; dy =  0; break;
+        case k8_SkKey: dx =  0; dy = -1; break;
+        case k6_SkKey: dx =  1; dy =  0; break;
+        case k2_SkKey: dx =  0; dy =  1; break;
+        case k4_SkKey: dx = -1; dy =  0; break;
+        case k7_SkKey: dx = -1; dy = -1; break;
+        case k9_SkKey: dx =  1; dy = -1; break;
+        case k3_SkKey: dx =  1; dy =  1; break;
+        case k1_SkKey: dx = -1; dy =  1; break;
+
         default:
             break;
     }
+
+    if (0xFF != dx && 0xFF != dy) {
+        this->changeOffset({SkIntToScalar(dx / 32.0f), SkIntToScalar(dy / 32.0f)});
+        return true;
+    }
+
     return this->INHERITED::onHandleKey(key);
 }
 
@@ -2048,6 +2071,9 @@ void SampleWindow::updateTitle() {
     title.prepend(fFlipAxis & kFlipAxis_Y ? "Y " : nullptr);
     title.prepend(gHintingStates[fHintingState].label);
 
+    if (fOffset.fX || fOffset.fY) {
+        title.prependf("(%.2f, %.2f) ", SkScalarToFloat(fOffset.fX), SkScalarToFloat(fOffset.fY));
+    }
     if (fZoomLevel) {
         title.prependf("{%.2f} ", SkScalarToFloat(fZoomLevel));
     }