From 0a68c4626db4a8f1b26a2d1fd10ff0c07b165d1c Mon Sep 17 00:00:00 2001
From: David Capello <davidcapello@gmail.com>
Date: Wed, 28 Dec 2016 11:38:28 -0300
Subject: [PATCH] Fix rendering issues with multiples of 3 zoom factors (fix
 #1349)

---
 src/render/render.cpp       | 12 +++++----
 src/render/render_tests.cpp | 54 +++++++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+), 5 deletions(-)

diff --git a/src/render/render.cpp b/src/render/render.cpp
index bfc447a06..73d8b33aa 100644
--- a/src/render/render.cpp
+++ b/src/render/render.cpp
@@ -422,7 +422,7 @@ void composite_image_general(
   double srcXDelta = 1.0 / sx;
   int srcWidth = src->width();
   for (int y=0; y<dstBounds.h; ++y, ++dstY) {
-    int srcY = (srcBounds.y+y) / sy;
+    int srcY = (srcBounds.y+double(y)) / sy;
     double srcX = srcXStart;
     int oldSrcX;
 
@@ -435,17 +435,19 @@ void composite_image_general(
     int dstX = dstBounds.x;
 #endif
 
-    for (int x=0; x<dstBounds.w; ++x, ++dstPtr) {
+    for (int x=0; x<dstBounds.w; ++dstPtr) {
       ASSERT(dstX >= 0 && dstX < dst->width());
       ASSERT(srcX >= 0 && srcX < src->width());
 
       *dstPtr = blender(*dstPtr, *srcPtr, opacity);
+      ++x;
 
       oldSrcX = int(srcX);
-      srcX += srcXDelta;
-      if (srcX >= srcWidth)
+      srcX = srcXStart + srcXDelta*x;
+      if (srcX >= srcWidth) {
         break;
-      srcPtr += (int(srcX) - oldSrcX);
+      }
+      srcPtr += int(srcX - oldSrcX);
 
 #if _DEBUG
       ++dstX;
diff --git a/src/render/render_tests.cpp b/src/render/render_tests.cpp
index 94345802c..8b8d16152 100644
--- a/src/render/render_tests.cpp
+++ b/src/render/render_tests.cpp
@@ -212,6 +212,60 @@ TEST(Render, ZoomAndDstBounds)
     0, 0, 0, 0);
 }
 
+TEST(Render, BugWithMultiplesOf3ZoomFactors)
+{
+  Context ctx;
+  Document* doc = ctx.documents().add(4, 4, ColorMode::RGB);
+  Image* src = doc->sprite()->root()->firstLayer()->cel(0)->image();
+  clear_image(src, 0);
+  draw_line(src, 0, 0, 3, 3, rgba(255, 0, 0, 255));
+
+  // Added other factors (like 1, 2, 4, etc.) too
+  int zooms[] = { 1, 2, 3, 4, 6, 8, 9, 12, 15, 16, 18, 21, 24, 27,
+                  30, 32, 33, 36, 39, 42, 45, 48, 51, 54, 57, 60,
+                  63, 66, 69, 72, 75, 78, 81 };
+  for (int zoom : zooms) {
+    base::UniquePtr<Image> dst(Image::create(IMAGE_RGB, 4*zoom, 4*zoom));
+    clear_image(dst, 0);
+
+    Render render;
+    render.setBgType(BgType::CHECKED);
+    render.setBgZoom(false);
+    render.setBgColor1(rgba(128, 128, 128, 255));
+    render.setBgColor2(rgba(64, 64, 64, 255));
+    render.setBgCheckedSize(gfx::Size(2, 2));
+    render.setProjection(Projection(PixelRatio(1, 1), Zoom(zoom, 1)));
+    render.renderSprite(
+      dst, doc->sprite(), frame_t(0),
+      gfx::Clip(0, 0, 0, 0, 4*zoom, 4*zoom));
+
+    for (int y=0; y<dst->height(); ++y) {
+      for (int x=0; x<dst->width(); ++x) {
+        color_t c = get_pixel(dst, x, y);
+
+        if (x / zoom == y / zoom) {
+          EXPECT_EQ(c, rgba(255, 0, 0, 255))
+            << " zoom=" << zoom << " x=" << x << " y=" << y;
+        }
+        else {
+          EXPECT_NE(c, rgba(255, 0, 0, 255))
+            << " zoom=" << zoom << " x=" << x << " y=" << y;
+
+          int gridBg = ((x / 2) + (y / 2)) % 2;
+          if (gridBg == 0) {
+            EXPECT_EQ(c, rgba(128, 128, 128, 255))
+              << " zoom=" << zoom << " x=" << x << " y=" << y;
+          }
+          else {
+            EXPECT_EQ(c, rgba(64, 64, 64, 255))
+              << " zoom=" << zoom << " x=" << x << " y=" << y;
+          }
+        }
+      }
+    }
+  }
+}
+
 int main(int argc, char** argv)
 {
   ::testing::InitGoogleTest(&argc, argv);