1 files changed, 104 insertions, 0 deletions
diff --git a/app/src/test/java/org/terst/feedreader/ui/ImageZoomTest.kt b/app/src/test/java/org/terst/feedreader/ui/ImageZoomTest.kt
index 81ecc33..3f7078d 100644
--- a/app/src/test/java/org/terst/feedreader/ui/ImageZoomTest.kt
+++ b/app/src/test/java/org/terst/feedreader/ui/ImageZoomTest.kt
@@ -169,6 +169,110 @@ class ImageZoomTest {
     }
 
     @Test
+    fun `a drag on a zoomed image pans it`() {
+        // The regression this function exists for: the viewer computed its pan bounds from
+        // values captured once at composition (viewport still zero, image not yet decoded),
+        // which pinned every offset to 0 -- a zoomed image simply refused to pan.
+        val panned = imageZoomTransform(
+            ImageZoomState(scale = 2f),
+            viewportSize = 1000f to 1000f,
+            intrinsicSize = 1000f to 1000f,
+            pan = -100f to -50f,
+            gestureZoom = 1f
+        )
+        assertEquals(2f, panned.scale, 0.001f)
+        assertEquals(-100f, panned.offsetX, 0.001f)
+        assertEquals(-50f, panned.offsetY, 0.001f)
+    }
+
+    @Test
+    fun `a drag on an unzoomed image leaves it where it is`() {
+        val panned = imageZoomTransform(
+            ImageZoomState(scale = 1f),
+            viewportSize = 1000f to 1000f,
+            intrinsicSize = 1000f to 1000f,
+            pan = 100f to 100f,
+            gestureZoom = 1f
+        )
+        assertEquals(0f, panned.offsetX, 0.001f)
+        assertEquals(0f, panned.offsetY, 0.001f)
+    }
+
+    @Test
+    fun `a pan stops at the edge of the scaled image`() {
+        val panned = imageZoomTransform(
+            ImageZoomState(scale = 2f, offsetX = 400f),
+            viewportSize = 1000f to 1000f,
+            intrinsicSize = 1000f to 1000f,
+            pan = 300f to 0f,
+            gestureZoom = 1f
+        )
+        assertEquals(500f, panned.offsetX, 0.001f)
+    }
+
+    @Test
+    fun `a pinch zooms and clamps the existing pan to the new scale`() {
+        val zoomedOut = imageZoomTransform(
+            ImageZoomState(scale = 2f, offsetX = 500f, offsetY = 500f),
+            viewportSize = 1000f to 1000f,
+            intrinsicSize = 1000f to 1000f,
+            pan = 0f to 0f,
+            gestureZoom = 0.1f
+        )
+        assertEquals(1f, zoomedOut.scale, 0.001f)
+        assertEquals(0f, zoomedOut.offsetX, 0.001f)
+        assertEquals(0f, zoomedOut.offsetY, 0.001f)
+    }
+
+    @Test
+    fun `a letterboxed image pans along its long axis only`() {
+        // A 2000x1000 photo fitted into a 1000x1000 viewport is 1000x500 on screen, so at 2x
+        // it fills the viewport exactly -- there's nothing above or below it to pan to, but
+        // dragging sideways still works.
+        val panned = imageZoomTransform(
+            ImageZoomState(scale = 2f),
+            viewportSize = 1000f to 1000f,
+            intrinsicSize = 2000f to 1000f,
+            pan = -200f to 300f,
+            gestureZoom = 1f
+        )
+        assertEquals(-200f, panned.offsetX, 0.001f)
+        assertEquals(0f, panned.offsetY, 0.001f)
+    }
+
+    @Test
+    fun `an image that hasn't reported its size yet can still be panned`() {
+        // Coil reports intrinsic size only once the image decodes; a pinch-and-drag before
+        // then is bounded by the viewport rather than refusing to move.
+        val panned = imageZoomTransform(
+            ImageZoomState(scale = 2f),
+            viewportSize = 1000f to 1000f,
+            intrinsicSize = 0f to 0f,
+            pan = -300f to 0f,
+            gestureZoom = 1f
+        )
+        assertEquals(-300f, panned.offsetX, 0.001f)
+    }
+
+    @Test
+    fun `double-tapping zooms in from the fitted size`() {
+        val zoomed = imageZoomDoubleTap(ImageZoomState(), 1000f to 1000f, 1000f to 1000f)
+        assertTrue(zoomed.scale > 1f)
+    }
+
+    @Test
+    fun `double-tapping a panned, zoomed image returns it to fitted and centered`() {
+        val reset = imageZoomDoubleTap(
+            ImageZoomState(scale = 3f, offsetX = 300f, offsetY = -200f),
+            1000f to 1000f,
+            1000f to 1000f
+        )
+        assertEquals(1f, reset.scale, 0.001f)
+        assertEquals(0f, reset.offsetX, 0.001f)
+        assertEquals(0f, reset.offsetY, 0.001f)
+    }
+
+    @Test
     fun `an image whose size isn't known yet is assumed to fill the viewport`() {
         // Coil only reports intrinsic size once the image has actually decoded; until then
         // panning has to be bounded by something, and the viewport is the safe guess.