Make image viewer truly full screen

app/androidApp/src/test/kotlin/com/example/aiapp/SessionImageTest.kt

@@ -5,6 +5,80 @@ import kotlin.test.Test
 import kotlin.test.assertEquals
 
 class SessionImageTest {
+    @Test
+    fun `a full-height image hides both bars`() {
+        assertEquals(
+            ViewerBars(status = true, navigation = true),
+            viewerBars(
+                imageWidth = 500,
+                imageHeight = 1000,
+                viewportWidth = 1000,
+                viewportHeight = 2000,
+                scale = 1f,
+                offset = Offset.Zero,
+                insets = ViewerBarInsets(status = 100, navigation = 100),
+            ),
+        )
+    }
+
+    @Test
+    fun `a letterboxed image leaves both bars visible`() {
+        assertEquals(
+            ViewerBars(),
+            viewerBars(
+                imageWidth = 1000,
+                imageHeight = 500,
+                viewportWidth = 1000,
+                viewportHeight = 2000,
+                scale = 1f,
+                offset = Offset.Zero,
+                insets = ViewerBarInsets(status = 100, navigation = 100),
+            ),
+        )
+    }
+
+    @Test
+    fun `panning into the status bar hides only that bar`() {
+        assertEquals(
+            ViewerBars(status = true),
+            viewerBars(
+                imageWidth = 1000,
+                imageHeight = 500,
+                viewportWidth = 1000,
+                viewportHeight = 2000,
+                scale = 2f,
+                offset = Offset(0f, -500f),
+                insets = ViewerBarInsets(status = 100, navigation = 100),
+            ),
+        )
+    }
+
+    @Test
+    fun `native scale reverses fitting a tall image`() {
+        assertEquals(
+            1.25f,
+            nativeScale(
+                imageWidth = 1000,
+                imageHeight = 2000,
+                viewportWidth = 1000,
+                viewportHeight = 1600,
+            ),
+        )
+    }
+
+    @Test
+    fun `native scale reverses enlarging a small image`() {
+        assertEquals(
+            0.5f,
+            nativeScale(
+                imageWidth = 500,
+                imageHeight = 500,
+                viewportWidth = 1000,
+                viewportHeight = 1000,
+            ),
+        )
+    }
+
     @Test
     fun `zoom keeps the region panned to in the center`() {
         assertEquals(