RFC for adding a cache for MinSize

widget/entry.go

@@ -95,7 +95,6 @@ type Entry struct {
 	ActionItem      fyne.CanvasObject `json:"-"`
 	binder          basicBinder
 	conversionError error
-	minCache        fyne.Size
 	multiLineRows   int // override global default number of visible lines
 
 	// undoStack stores the data necessary for undo/redo functionality
@@ -401,9 +400,7 @@ func (e *Entry) KeyUp(key *fyne.KeyEvent) {
 //
 // Implements: fyne.Widget
 func (e *Entry) MinSize() fyne.Size {
-	e.propertyLock.RLock()
-	cached := e.minCache
-	e.propertyLock.RUnlock()
+	cached := e.GetMinSizeCache()
 	if !cached.IsZero() {
 		return cached
 	}
@@ -412,17 +409,15 @@ func (e *Entry) MinSize() fyne.Size {
 
 	th := e.Theme()
 	iconSpace := th.Size(theme.SizeNameInlineIcon) + th.Size(theme.SizeNameLineSpacing)
-	min := e.BaseWidget.MinSize()
+	min := e.BaseWidget.MinSizeFromRenderer()
 	if e.ActionItem != nil {
 		min = min.Add(fyne.NewSize(iconSpace, 0))
 	}
 	if e.Validator != nil {
 		min = min.Add(fyne.NewSize(iconSpace, 0))
 	}
 
-	e.propertyLock.Lock()
-	e.minCache = min
-	e.propertyLock.Unlock()
+	e.SetMinSizeCache(min)
 	return min
 }
 
@@ -488,14 +483,6 @@ func (e *Entry) Redo() {
 	e.Refresh()
 }
 
-func (e *Entry) Refresh() {
-	e.propertyLock.Lock()
-	e.minCache = fyne.Size{}
-	e.propertyLock.Unlock()
-
-	e.BaseWidget.Refresh()
-}
-
 // SelectedText returns the text currently selected in this Entry.
 // If there is no selection it will return the empty string.
 func (e *Entry) SelectedText() string {

widget/widget.go

@@ -16,6 +16,7 @@ import (
 // BaseWidget provides a helper that handles basic widget behaviours.
 type BaseWidget struct {
 	size     async.Size
+	minCache async.Size
 	position async.Position
 	Hidden   bool
 
@@ -69,6 +70,16 @@ func (w *BaseWidget) Move(pos fyne.Position) {
 
 // MinSize for the widget - it should never be resized below this value.
 func (w *BaseWidget) MinSize() fyne.Size {
+	minCache := w.minCache.Load()
+	if !minCache.IsZero() {
+		return minCache
+	}
+
+	return w.MinSizeFromRenderer()
+}
+
+// MinSizeFromRenderer returns the MinSize has defined by this widget's renderer.
+func (w *BaseWidget) MinSizeFromRenderer() fyne.Size {
 	impl := w.super()
 
 	r := cache.Renderer(impl)
@@ -88,6 +99,18 @@ func (w *BaseWidget) Visible() bool {
 	return !w.Hidden
 }
 
+// GetMinSizeCache returns the currently cached MinSize value.
+// This value is set to zero on calling Refresh().
+func (w *BaseWidget) GetMinSizeCache() fyne.Size {
+	return w.minCache.Load()
+}
+
+// SetMinSizeCache updates the internal cache for the MinSize.
+// This cached value will be used until the next Refresh.
+func (w *BaseWidget) SetMinSizeCache(cache fyne.Size) {
+	w.minCache.Store(cache)
+}
+
 // Show this widget so it becomes visible
 func (w *BaseWidget) Show() {
 	if w.Visible() {
@@ -123,6 +146,8 @@ func (w *BaseWidget) Refresh() {
 		return
 	}
 
+	w.minCache.Store(fyne.Size{})
+
 	w.propertyLock.Lock()
 	w.themeCache = nil
 	w.propertyLock.Unlock()