Stop subwindow dragging when mouse releases outside the header

.github/workflows/build.yml

@@ -59,6 +59,7 @@ jobs:
         run: |
           nim r tests/test_textboxes.nim
           nim r -d:silkyTesting -d:nimTypeNames tests/test_inputs.nim
+          nim r -d:silkyTesting tests/test_subwindow.nim
           nim r tests/test_atlas_png.nim
           nim r -d:silkyTesting tests/test_layout.nim
           nim r -d:silkyTesting tests/test_layout_regressions.nim

src/silky/widgets.nim

@@ -163,7 +163,10 @@ proc subWindowStart*(
     titleBarInteraction = sk.interact(titleBarRect, true)
 
   case titleBarInteraction
-  of Disabled, None, Error, ReleasedOutside:
+  of Disabled, None, Error:
+    sk.draw9Patch("header.9patch", sk.theme.headerPatch, sk.pos, sk.size)
+  of ReleasedOutside:
+    subWindowState.dragging = false
     sk.draw9Patch("header.9patch", sk.theme.headerPatch, sk.pos, sk.size)
   of Pressed:
     subWindowState.dragOffset = sk.mousePos - subWindowState.pos

tests/test_subwindow.nim

@@ -0,0 +1,67 @@
+import
+  std/options,
+  vmath,
+  silky
+
+when not defined(silkyTesting):
+  {.error: "Compile with -d:silkyTesting".}
+
+let builder = newAtlasBuilder(1024, 4)
+builder.addDir("tests/data/", "tests/data/")
+builder.addFont("tests/data/IBMPlexSans-Regular.ttf", "Default", 18.0)
+
+var show = true
+
+proc drawSubwindow(sk: Silky, window: Window) =
+  ## Exercise the real title-bar interaction and balanced window layout.
+  let state = sk.subWindowStart(
+    window, "Drag regression", show, some(vec2(100, 100)), some(vec2(300, 200))
+  )
+  sk.subWindowEnd(window, state)
+
+block:
+  subWindowStates.clear()
+  var harness = newTestHarness(builder.atlas)
+  let window = harness.window
+  window.moveMouse(150, 110)
+  discard harness.pumpFrame(drawSubwindow, 2)
+  let state = subWindowStates["Drag regression"]
+  window.pressButton(MouseLeft)
+  discard harness.pumpFrame(drawSubwindow)
+  doAssert state.dragging, "Pressing the header must start dragging"
+  doAssert state.pos == vec2(100, 100)
+
+  # A held drag must keep working even when the pointer leaves the old header.
+  window.moveMouse(210, 160)
+  discard harness.pumpFrame(drawSubwindow)
+  doAssert state.dragging
+  doAssert state.pos == vec2(160, 150)
+  let heldPosition = state.pos
+
+  # Release well outside the current header before another frame is drawn.
+  window.moveMouse(450, 350)
+  window.releaseButton(MouseLeft)
+  discard harness.pumpFrame(drawSubwindow)
+  doAssert not state.dragging, "Releasing outside the header must end dragging"
+  doAssert state.pos == heldPosition, "A released drag must not move the window"
+
+  window.moveMouse(600, 450)
+  discard harness.pumpFrame(drawSubwindow, 2)
+  doAssert state.pos == heldPosition,
+    "Pointer movement after an outside release must not drag the window"
+
+  # A new drag starts from the last held position, not a stale drag offset.
+  window.moveMouse(230, 160)
+  discard harness.pumpFrame(drawSubwindow, 2)
+  window.pressButton(MouseLeft)
+  discard harness.pumpFrame(drawSubwindow)
+  doAssert state.dragging and state.pos == heldPosition
+  window.moveMouse(260, 180)
+  discard harness.pumpFrame(drawSubwindow)
+  doAssert state.pos == heldPosition + vec2(30, 20)
+  discard harness.pumpFrame(drawSubwindow, 2)
+  window.releaseButton(MouseLeft)
+  discard harness.pumpFrame(drawSubwindow)
+  doAssert not state.dragging, "Releasing over the header must still end dragging"
+
+  echo "Subwindow outside release stops dragging and the next drag starts cleanly"