feat: Add top and bottom offset for content; Make horizontal scrollbar usable

TextControlBox-TestApp/MainWindow.xaml.cs

@@ -22,6 +22,8 @@ public MainWindow()
             textbox.NumberOfSpacesForTab = 4;
             textbox.ShowWhitespaceCharacters = true;
 
+            textbox.ContentVerticalScrollOffset = new TextControlBoxNS.Models.Structs.VerticalScrollOffset(100, 100);
+
             SetWindowTheme(this, ElementTheme.Dark);
 
             textbox.LinkClicked += Textbox_LinkClicked;

TextControlBox/Core/CoreTextControlBox.xaml

@@ -23,6 +23,10 @@
             <ColumnDefinition Width="auto"/>
             <ColumnDefinition Width="*"/>
         </Grid.ColumnDefinitions>
+        <Grid.RowDefinitions>
+            <RowDefinition Height="*"/>
+            <RowDefinition Height="auto"/>
+        </Grid.RowDefinitions>
         <xaml:CanvasControl
                     Grid.Column="0"
                     x:Name="Canvas_LineNumber"
@@ -61,8 +65,8 @@
                         VerticalAlignment="Stretch"/>
 
             <ScrollBar Grid.Column="2" PointerEntered="Scrollbar_PointerEntered" PointerExited="Scrollbar_PointerExited" SmallChange="10" Maximum="0" LargeChange="100" Minimum="0" x:Name="VerticalScrollbar" Value="0" IndicatorMode="MouseIndicator" Background="Transparent" HorizontalAlignment="Right" Orientation="Vertical" VerticalAlignment="Stretch"/>
-            <ScrollBar PointerEntered="Scrollbar_PointerEntered" PointerExited="Scrollbar_PointerExited" SmallChange="10" LargeChange="100" Minimum="0" Maximum="0" x:Name="HorizontalScrollbar" Value="0" IndicatorMode="MouseIndicator" Background="Transparent" HorizontalAlignment="Stretch" Orientation="Horizontal" VerticalAlignment="Bottom"/>
         </Grid>
+        <ScrollBar Grid.Row="2" Grid.ColumnSpan="2" PointerEntered="Scrollbar_PointerEntered" PointerExited="Scrollbar_PointerExited" SmallChange="10" LargeChange="100" Minimum="0" Maximum="0" x:Name="HorizontalScrollbar" Value="0" IndicatorMode="MouseIndicator" Background="Transparent" HorizontalAlignment="Stretch" Orientation="Horizontal" VerticalAlignment="Bottom"/>
         <controls:InputHandlerControl x:Name="inputHandler" GotFocus="InputManager_GotFocus" LostFocus="InputManager_LostFocus" PreviewKeyDown="InputHandler_KeyDown" TextEntered="InputHandler_TextEntered" Grid.Column="1" Opacity="0" Width="0" Height="0"/>
     </Grid>
 </UserControl>

TextControlBox/Core/CoreTextControlBox.xaml.cs

@@ -14,6 +14,7 @@
 using TextControlBoxNS.Languages;
 using TextControlBoxNS.Models;
 using TextControlBoxNS.Models.Enums;
+using TextControlBoxNS.Models.Structs;
 using Windows.ApplicationModel.DataTransfer;
 using Windows.Foundation;
 using Windows.System;
@@ -985,6 +986,23 @@ public void EndActionGroup()
     }
     public bool IsGroupingActions => undoRedo.IsGroupingActions;
 
+    private VerticalScrollOffset _ContentVerticalScrollOffset = new(0);
+
+    public VerticalScrollOffset ContentVerticalScrollOffset
+    {
+        get => _ContentVerticalScrollOffset;
+        set
+        {
+            _ContentVerticalScrollOffset = value;
+
+            textRenderer.UpdateScrollOffset(value);
+            Canvas_Text.UpdateLayout();
+            Canvas_Selection.UpdateLayout();
+            Canvas_Cursor.UpdateLayout();
+            Canvas_LineNumber.UpdateLayout();
+        }
+    }
+
     public bool EnableSyntaxHighlighting { get; set; } = true;
 
     public SyntaxHighlightLanguage SyntaxHighlighting

TextControlBox/Core/PointerActionsManager.cs

@@ -393,7 +393,7 @@ public void PointerWheelAction(ZoomManager zoomManager, PointerRoutedEventArgs e
         {
             scrollManager.verticalScrollBar.Value -= (delta * scrollManager._VerticalScrollSensitivity) / scrollManager.DefaultVerticalScrollSensitivity;
             //Only update when a line was scrolled
-            if ((int)(scrollManager.verticalScrollBar.Value / textRenderer.SingleLineHeight * scrollManager.DefaultVerticalScrollSensitivity) != textRenderer.NumberOfStartLine)
+            if ((int)(scrollManager.verticalScrollBar.Value / textRenderer.SingleLineHeight * scrollManager.DefaultVerticalScrollSensitivity + textRenderer.VerticalDrawOffset) != textRenderer.NumberOfStartLine)
             {
                 needsUpdate = true;
             }

TextControlBox/Core/Renderer/CursorRenderer.cs

@@ -80,7 +80,7 @@ public void Draw(CanvasControl canvasText, CanvasControl canvasCursor, CanvasDra
         float singleLineHeight = textRenderer.SingleLineHeight;
 
         //Calculate the distance to the top for the cursorposition and render the cursor
-        float renderPosY = (float)((cursorManager.LineNumber - startLine) * singleLineHeight) + singleLineHeight / scrollManager.DefaultVerticalScrollSensitivity;
+        float renderPosY = (float)((cursorManager.LineNumber - startLine) * singleLineHeight) + singleLineHeight / scrollManager.DefaultVerticalScrollSensitivity + textRenderer.VerticalDrawOffset;
 
         //Out of display-region:
         if (renderPosY > linesToRender * singleLineHeight || renderPosY < 0)

TextControlBox/Core/Renderer/LineNumberRenderer.cs

@@ -76,7 +76,7 @@ public void Draw(CanvasControl canvas, CanvasDrawEventArgs args, float spaceBetw
 
             OldLineNumberTextToRender = LineNumberTextToRender;
             LineNumberTextLayout = textLayoutManager.CreateTextLayout(canvas, LineNumberTextFormat, LineNumberTextToRender, posX, (float)canvas.Size.Height);
-            args.DrawingSession.DrawTextLayout(LineNumberTextLayout, 10, textRenderer.SingleLineHeight, designHelper.LineNumberColorBrush);
+            args.DrawingSession.DrawTextLayout(LineNumberTextLayout, 10, textRenderer.VerticalDrawOffset + textRenderer.SingleLineHeight, designHelper.LineNumberColorBrush);
         }
 
         public void CreateLineNumberTextFormat()

TextControlBox/Core/Renderer/SelectionRenderer.cs

@@ -191,7 +191,7 @@ public void Draw(CanvasControl canvasSelection, CanvasDrawEventArgs args)
                     textRenderer.DrawnTextLayout,
                     args,
                     (float)-scrollManager.HorizontalScroll,
-                    textRenderer.SingleLineHeight / scrollManager.DefaultVerticalScrollSensitivity,
+                    textRenderer.SingleLineHeight / scrollManager.DefaultVerticalScrollSensitivity + textRenderer.VerticalDrawOffset,
                     textRenderer.NumberOfStartLine,
                     textRenderer.NumberOfRenderedLines,
                     zoomManager.ZoomedFontSize,

TextControlBox/Core/Renderer/TextRenderer.cs

@@ -8,6 +8,7 @@
 using System.Runtime.InteropServices;
 using TextControlBoxNS.Core.Text;
 using TextControlBoxNS.Helper;
+using TextControlBoxNS.Models.Structs;
 using Windows.Foundation;
 
 namespace TextControlBoxNS.Core.Renderer;
@@ -27,6 +28,10 @@ internal class TextRenderer
     public int NumberOfRenderedLines = 0;
     public string RenderedText = "";
     public string OldRenderedText = null;
+    public float VerticalDrawOffset { get; private set; } = 0;
+
+    public double TopScrollOffset { get; private set; } = 0;
+    public double BottomScrollOffset { get; private set; } = 0;
 
     private CursorManager cursorManager;
     private TextManager textManager;
@@ -75,6 +80,14 @@ public void Init(
         this.invisibleCharactersRenderer = invisibleCharactersRenderer;
         this.linkRenderer = linkRenderer;
         this.linkHighlightManager = linkHighlightManager;
+
+        UpdateScrollOffset(coreTextbox.ContentVerticalScrollOffset);
+    }
+
+    public void UpdateScrollOffset(VerticalScrollOffset verticalScrollOffset)
+    {
+        this.TopScrollOffset = verticalScrollOffset.Top;
+        this.BottomScrollOffset = verticalScrollOffset.Bottom;
     }
 
     //Check whether the current line is outside the bounds of the visible area
@@ -99,24 +112,49 @@ public void UpdateCurrentLineTextLayout(CanvasControl canvasText)
         var singleLineHeight = SingleLineHeight;
 
         //Measure text position and apply the value to the scrollbar
-        scrollManager.verticalScrollBar.Maximum = ((textManager.LinesCount + 1) * singleLineHeight - scrollGrid.ActualHeight) / scrollManager.DefaultVerticalScrollSensitivity;
+        scrollManager.verticalScrollBar.Maximum = ((textManager.LinesCount + 1) * singleLineHeight - scrollGrid.ActualHeight + BottomScrollOffset + TopScrollOffset) / scrollManager.DefaultVerticalScrollSensitivity;
         scrollManager.verticalScrollBar.ViewportSize = coreTextbox.canvasText.ActualHeight;
 
         //Calculate number of lines that need to be rendered
         int linesToRenderCount = (int)(coreTextbox.canvasText.ActualHeight / singleLineHeight);
-        linesToRenderCount = Math.Min(linesToRenderCount, textManager.LinesCount);
+        linesToRenderCount = Math.Min(Math.Max(linesToRenderCount, 1), textManager.LinesCount);
 
-        int startLine = (int)((scrollManager.VerticalScroll * scrollManager.DefaultVerticalScrollSensitivity) / singleLineHeight);
+        int startLine = (int)(((scrollManager.VerticalScroll - VerticalDrawOffset) * scrollManager.DefaultVerticalScrollSensitivity - TopScrollOffset) / singleLineHeight);
         startLine = Math.Min(startLine, textManager.LinesCount);
 
+        if (startLine < 0) startLine = 0;
+
         int linesToRender = Math.Min(linesToRenderCount, textManager.LinesCount - startLine);
 
         return (startLine, linesToRender);
     }
 
+    public float CalculateDrawOffset()
+    {
+        double verticalScroll = scrollManager.VerticalScroll;
+
+        double scrollCoeff = scrollManager.verticalScrollBar.Maximum / scrollManager.VerticalScroll;
+
+        double realScrollPosition = verticalScroll * scrollManager.DefaultVerticalScrollSensitivity - TopScrollOffset;
+        double preCalcOffset = realScrollPosition < 0 ? -realScrollPosition : SingleLineHeight;
+
+        float drawOffset = (float)(preCalcOffset < SingleLineHeight ? SingleLineHeight : Math.Floor(preCalcOffset / SingleLineHeight) * SingleLineHeight);
+
+        if (drawOffset > SingleLineHeight)
+        {
+            if (scrollCoeff == 1)
+            {
+                drawOffset = SingleLineHeight;
+            }
+        }
+        return drawOffset - SingleLineHeight;
+    }
+
 
     public void Draw(CanvasControl canvasText, CanvasDrawEventArgs args)
     {
+        VerticalDrawOffset = CalculateDrawOffset();
+
         //Create resources and layouts:
         if (NeedsTextFormatUpdate || TextFormat == null || lineNumberRenderer.LineNumberTextFormat == null)
         {
@@ -171,13 +209,13 @@ public void Draw(CanvasControl canvasText, CanvasDrawEventArgs args)
                     searchManager.MatchingSearchLines,
                     searchManager.searchParameter.SearchExpression,
                     (float)-scrollManager.HorizontalScroll,
-                    SingleLineHeight / scrollManager.DefaultVerticalScrollSensitivity,
+                    SingleLineHeight / scrollManager.DefaultVerticalScrollSensitivity + VerticalDrawOffset,
                     designHelper._Design.SearchHighlightColor
                     );
 
-            ccls.DrawTextLayout(DrawnTextLayout, (float)-scrollManager.HorizontalScroll, SingleLineHeight, designHelper.TextColorBrush);
+            ccls.DrawTextLayout(DrawnTextLayout, (float)-scrollManager.HorizontalScroll, VerticalDrawOffset + SingleLineHeight, designHelper.TextColorBrush);
 
-            invisibleCharactersRenderer.DrawTabsAndSpaces(args, ccls, RenderedText, DrawnTextLayout, SingleLineHeight);
+            invisibleCharactersRenderer.DrawTabsAndSpaces(args, ccls, RenderedText, DrawnTextLayout, VerticalDrawOffset + SingleLineHeight);
         }
         args.DrawingSession.DrawImage(canvasCommandList);
 
@@ -189,5 +227,7 @@ public void Draw(CanvasControl canvasText, CanvasDrawEventArgs args)
         {
             canvasUpdateManager.UpdateLineNumbers();
         }
+        canvasUpdateManager.UpdateSelection(); // Possible bad for performanse
+        canvasUpdateManager.UpdateCursor(); // Possible bad for performanse
     }
 }

TextControlBox/Core/ScrollManager.cs

@@ -57,7 +57,7 @@ internal void HorizontalScrollBar_Scroll(object sender, ScrollEventArgs e)
     internal void VerticalScrollBar_Scroll(object sender, ScrollEventArgs e)
     {
         //only update when a line was scrolled
-        if ((int)(verticalScrollBar.Value / textRenderer.SingleLineHeight * DefaultVerticalScrollSensitivity) != textRenderer.NumberOfStartLine)
+        if ((int)(verticalScrollBar.Value / textRenderer.SingleLineHeight * DefaultVerticalScrollSensitivity + textRenderer.VerticalDrawOffset ) != textRenderer.NumberOfStartLine)
         {
             canvasHelper.UpdateAll();
         }
@@ -66,7 +66,7 @@ internal void VerticalScrollBar_Scroll(object sender, ScrollEventArgs e)
     public void UpdateWhenScrolled()
     {
         //only update when a line was scrolled
-        if ((int)(verticalScrollBar.Value / textRenderer.SingleLineHeight) != textRenderer.NumberOfStartLine)
+        if ((int)(verticalScrollBar.Value / textRenderer.SingleLineHeight + textRenderer.VerticalDrawOffset) != textRenderer.NumberOfStartLine)
         {
             canvasHelper.UpdateAll();
         }
@@ -133,10 +133,30 @@ public void ScrollPageDown()
     }
     public void UpdateScrollToShowCursor(bool update = true)
     {
-        if (textRenderer.NumberOfStartLine + textRenderer.NumberOfRenderedLines <= cursorManager.LineNumber)
-            verticalScrollBar.Value = (cursorManager.LineNumber - textRenderer.NumberOfRenderedLines + 1) * textRenderer.SingleLineHeight / DefaultVerticalScrollSensitivity;
+        double globalOffset = textRenderer.VerticalDrawOffset == 0 ? textRenderer.TopScrollOffset : 0;
+        double localOffset = textRenderer.VerticalDrawOffset;
+
+        if (cursorManager.LineNumber == 0)
+        {
+            verticalScrollBar.Value = 0;
+        }
+        else if (textRenderer.NumberOfStartLine + textRenderer.NumberOfRenderedLines <= cursorManager.LineNumber)
+        {
+            verticalScrollBar.Value = ((cursorManager.LineNumber - textRenderer.NumberOfRenderedLines + 1) * textRenderer.SingleLineHeight + globalOffset) / DefaultVerticalScrollSensitivity + localOffset;
+        }
         else if (textRenderer.NumberOfStartLine > cursorManager.LineNumber)
-            verticalScrollBar.Value = (cursorManager.LineNumber - 1) * textRenderer.SingleLineHeight / DefaultVerticalScrollSensitivity;
+        {
+            verticalScrollBar.Value = ((cursorManager.LineNumber - 1) * textRenderer.SingleLineHeight + globalOffset) / DefaultVerticalScrollSensitivity + localOffset;
+        }
+        else if (textRenderer.VerticalDrawOffset != 0)
+        {
+            int realLineDisplayedCount = (int)((verticalScrollBar.ViewportSize - textRenderer.VerticalDrawOffset) / textRenderer.SingleLineHeight);
+            if (realLineDisplayedCount <= cursorManager.LineNumber)
+            {
+                double offsetToMove = ((cursorManager.LineNumber - realLineDisplayedCount + 1) * textRenderer.SingleLineHeight);
+                verticalScrollBar.Value = ((cursorManager.LineNumber - 1) * textRenderer.SingleLineHeight) / DefaultVerticalScrollSensitivity + offsetToMove;
+            }
+        }
 
         if (update)
             canvasHelper.UpdateAll();

TextControlBox/Helper/CursorHelper.cs

@@ -14,7 +14,7 @@ internal class CursorHelper
     public static int GetCursorLineFromPoint(TextRenderer textRenderer, Point point)
     {
         //Calculate the relative linenumber, where the pointer was pressed at
-        int linenumber = (int)(point.Y / textRenderer.SingleLineHeight);
+        int linenumber = (int)((point.Y - textRenderer.VerticalDrawOffset) / textRenderer.SingleLineHeight);
         linenumber += textRenderer.NumberOfStartLine;
         return Math.Clamp(linenumber, 0, textRenderer.NumberOfStartLine + textRenderer.NumberOfRenderedLines - 1);
     }