Revert "Revert "render: cache SKPaint, and drawing contexts""

This reverts commit 3540ecc.

Views/Cursor.xaml.fs

@@ -33,6 +33,7 @@ type Cursor() as this =
     let mutable fgbrush: SolidColorBrush  = SolidColorBrush(Colors.White)
     let mutable spbrush: SolidColorBrush  = SolidColorBrush(Colors.Red)
     let mutable cursor_fb = AllocateFramebuffer (20.0) (20.0) 1.0
+    let mutable cursor_dc: Avalonia.Platform.IDrawingContextImpl = null
     let mutable cursor_fb_vm = CursorViewModel(Some -1)
     let mutable cursor_fb_s = 1.0
 
@@ -42,7 +43,9 @@ type Cursor() as this =
             cursor_fb_vm <- this.ViewModel.Clone()
             cursor_fb_s <- s
             cursor_fb.Dispose()
+            cursor_dc.Dispose()
             cursor_fb <- AllocateFramebuffer (cursor_fb_vm.Width + 50.0) (cursor_fb_vm.Height + 50.0) s
+            cursor_dc <- cursor_fb.CreateDrawingContext(null)
             true
         elif cursor_fb_vm.text <> this.ViewModel.text then
             cursor_fb_vm.text <- this.ViewModel.text
@@ -162,11 +165,9 @@ type Cursor() as this =
                     // deferred
                     let redraw = ensure_fb()
                     if redraw then
-                        let dc = cursor_fb.CreateDrawingContext(null)
-                        dc.PushClip(bounds)
-                        render_block dc
-                        dc.PopClip()
-                        dc.Dispose()
+                        cursor_dc.PushClip(bounds)
+                        render_block cursor_dc
+                        cursor_dc.PopClip()
                     ctx.DrawImage(cursor_fb, 1.0, Rect(0.0, 0.0, bounds.Width * scale, bounds.Height * scale), bounds)
             with
             | ex -> trace "cursor" "render exception: %s" <| ex.ToString()

Views/Editor.xaml.fs

@@ -38,19 +38,20 @@ type Editor() as this =
   static let RenderTickProperty = AvaloniaProperty.Register<Editor, int>("RenderTick")
 
   let mutable grid_fb: RenderTargetBitmap = null
+  let mutable grid_dc: IDrawingContextImpl = null
   let mutable grid_scale: float = 1.0
   let mutable grid_vm: EditorViewModel = Unchecked.defaultof<_>
 
   let mutable m_debug = States.ui_multigrid
-  let mutable m_alphaLUT: byte [] = Array.create 256 0uy
-  let mutable m_normalLUT: byte [] = Array.create 256 0uy
-  let mutable m_nullLUT: byte [] = Array.create 256 0uy
 
   let resizeFrameBuffer() =
     trace grid_vm "resizeFrameBuffer bufw=%A bufh=%A" grid_vm.BufferWidth grid_vm.BufferHeight
     grid_scale <- this.GetVisualRoot().RenderScaling
-    if grid_fb <> null then grid_fb.Dispose()
+    if grid_fb <> null then 
+      grid_fb.Dispose()
+      grid_dc.Dispose()
     grid_fb <- AllocateFramebuffer (grid_vm.BufferWidth) (grid_vm.BufferHeight) grid_scale
+    grid_dc <- grid_fb.CreateDrawingContext(null)
 
   //-------------------------------------------------------------------------
   //           = The rounding error of the rendering system =
@@ -77,6 +78,10 @@ type Editor() as this =
     let px = pt * grid_scale
     Point(Math.Ceiling px.X, Math.Ceiling px.Y) / grid_scale
 
+  let mutable fgpaint = null
+  let mutable bgpaint = null
+  let mutable sppaint = null
+
   let drawBuffer (ctx: IDrawingContextImpl) row col colend hlid (str: string list) (issym: bool) =
 
     let x =
@@ -88,9 +93,10 @@ type Editor() as this =
     let fg, bg, sp, attrs = theme.GetDrawAttrs hlid
     let shaper, typeface = GetTypeface(x, attrs.italic, attrs.bold, font, fontwide)
 
-    use fgpaint = new SKPaint()
-    use bgpaint = new SKPaint()
-    use sppaint = new SKPaint()
+    if fgpaint = null then
+      fgpaint <- new SKPaint()
+      bgpaint <- new SKPaint()
+      sppaint <- new SKPaint()
     SetForegroundBrush(fgpaint, fg, typeface, fontsize)
 
     let nr_col =
@@ -234,12 +240,6 @@ type Editor() as this =
 
   do
 
-    // setup color filter LUTs
-    for i = 0 to 255 do
-      m_alphaLUT.[i] <- 0uy
-      m_normalLUT.[i] <- byte i
-    m_alphaLUT.[255] <- 255uy
-
     this.Watch
       [ this.GetObservable(Editor.DataContextProperty)
         |> Observable.ofType
@@ -270,7 +270,6 @@ type Editor() as this =
         let regions = dirty.Regions()
         trace grid_vm "drawing %d regions" regions.Count
         let timer = System.Diagnostics.Stopwatch.StartNew()
-        use grid_dc = grid_fb.CreateDrawingContext(null)
         grid_dc.PushClip(Rect this.Bounds.Size)
         for r in regions do
           for row = r.row to r.row_end - 1 do