fix fyne-io#1354: switching overlays no longer removes focus from pre…

…vious focus manager

Thus the focused element in the content stays highlighted while a pop-up
menu is opened. Also the focused element stays highlighted if the menu
is opened.
However, the _one_ focus for keyboard events is moved to the overlay on top.

internal/driver/glfw/canvas.go

@@ -388,18 +388,10 @@ func (c *glCanvas) objectTrees() []fyne.CanvasObject {
 	return trees
 }
 
-func (c *glCanvas) overlayChanged(focusMgr, prevFocusMgr *app.FocusManager) {
+func (c *glCanvas) overlayChanged() {
 	c.Lock()
 	defer c.Unlock()
 	c.dirty = true
-	if prevFocusMgr == nil {
-		prevFocusMgr = c.focusMgr
-	}
-	if focusMgr == nil {
-		focusMgr = c.focusMgr
-	}
-	prevFocusMgr.FocusLost()
-	focusMgr.FocusGained()
 }
 
 func (c *glCanvas) paint(size fyne.Size) {

internal/driver/glfw/canvas_test.go

@@ -188,26 +188,26 @@ func TestGlCanvas_FocusHandlingWhenAddingAndRemovingOverlays(t *testing.T) {
 	assert.True(t, ce2.focused)
 
 	c.Overlays().Add(overlay1)
-	ctxt := "adding overlay removes focus from content"
+	ctxt := "adding overlay changes focus handler but does not remove focus from content"
 	assert.Nil(t, c.Focused(), ctxt)
-	assert.False(t, ce2.focused, ctxt)
+	assert.True(t, ce2.focused, ctxt)
 
 	c.FocusNext()
 	ctxt = "changing focus affects overlay instead of content"
 	assert.Equal(t, o1e1, c.Focused(), ctxt)
 	assert.False(t, ce1.focused, ctxt)
-	assert.False(t, ce2.focused, ctxt)
+	assert.True(t, ce2.focused, ctxt)
 	assert.True(t, o1e1.focused, ctxt)
 
 	c.Overlays().Add(overlay2)
-	ctxt = "adding overlay removes focus from previous overlay"
+	ctxt = "adding overlay changes focus handler but does not remove focus from previous overlay"
 	assert.Nil(t, c.Focused(), ctxt)
-	assert.False(t, o1e1.focused, ctxt)
+	assert.True(t, o1e1.focused, ctxt)
 
 	c.FocusPrevious()
 	ctxt = "changing focus affects top overlay only"
 	assert.Equal(t, o2e2, c.Focused(), ctxt)
-	assert.False(t, o1e1.focused, ctxt)
+	assert.True(t, o1e1.focused, ctxt)
 	assert.False(t, o1e2.focused, ctxt)
 	assert.True(t, o2e2.focused, ctxt)
 
@@ -217,9 +217,9 @@ func TestGlCanvas_FocusHandlingWhenAddingAndRemovingOverlays(t *testing.T) {
 	assert.True(t, o2e1.focused)
 
 	c.Overlays().Remove(overlay2)
-	ctxt = "removing overlay removes focus from removed overlay and restores focus on new top overlay"
+	ctxt = "removing overlay restores focus handler from previous overlay but does not remove focus from removed overlay"
 	assert.Equal(t, o1e1, c.Focused(), ctxt)
-	assert.False(t, o2e1.focused, ctxt)
+	assert.True(t, o2e1.focused, ctxt)
 	assert.False(t, o2e2.focused, ctxt)
 	assert.True(t, o1e1.focused, ctxt)
 
@@ -229,10 +229,10 @@ func TestGlCanvas_FocusHandlingWhenAddingAndRemovingOverlays(t *testing.T) {
 	assert.True(t, o1e2.focused)
 
 	c.Overlays().Remove(overlay1)
-	ctxt = "removing last overlay removes focus from removed overlay and restores focus on content"
+	ctxt = "removing last overlay restores focus handler from content but does not remove focus from removed overlay"
 	assert.Equal(t, ce2, c.Focused(), ctxt)
 	assert.False(t, o1e1.focused, ctxt)
-	assert.False(t, o1e2.focused, ctxt)
+	assert.True(t, o1e2.focused, ctxt)
 	assert.True(t, ce2.focused, ctxt)
 }
 

internal/overlay_stack.go

@@ -9,7 +9,7 @@ import (
 
 // OverlayStack implements fyne.OverlayStack
 type OverlayStack struct {
-	OnChange      func(focusMgr, prevFocusMgr *app.FocusManager)
+	OnChange      func()
 	focusManagers []*app.FocusManager
 	overlays      []fyne.CanvasObject
 	propertyLock  sync.RWMutex
@@ -24,12 +24,14 @@ func (s *OverlayStack) Add(overlay fyne.CanvasObject) {
 	s.propertyLock.Lock()
 	defer s.propertyLock.Unlock()
 
-	defer s.notifyAboutChange(s.topFocusManager())
 	if overlay == nil {
 		return
 	}
 	s.overlays = append(s.overlays, overlay)
 	s.focusManagers = append(s.focusManagers, app.NewFocusManager(overlay))
+	if s.OnChange != nil {
+		s.OnChange()
+	}
 }
 
 // List returns all overlays on the stack from bottom to top.
@@ -49,14 +51,16 @@ func (s *OverlayStack) Remove(overlay fyne.CanvasObject) {
 	s.propertyLock.Lock()
 	defer s.propertyLock.Unlock()
 
-	defer s.notifyAboutChange(s.topFocusManager())
 	for i, o := range s.overlays {
 		if o == overlay {
 			s.overlays = s.overlays[:i]
 			s.focusManagers = s.focusManagers[:i]
 			break
 		}
 	}
+	if s.OnChange != nil {
+		s.OnChange()
+	}
 }
 
 // Top returns the top-most overlay of the stack.
@@ -79,13 +83,6 @@ func (s *OverlayStack) TopFocusManager() *app.FocusManager {
 	return s.topFocusManager()
 }
 
-func (s *OverlayStack) notifyAboutChange(pfm *app.FocusManager) {
-	if s.OnChange == nil {
-		return
-	}
-	s.OnChange(s.topFocusManager(), pfm)
-}
-
 func (s *OverlayStack) topFocusManager() *app.FocusManager {
 	var fm *app.FocusManager
 	if len(s.focusManagers) > 0 {