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feat(textbox): add support for up/down arrow keys preserving the care…
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…t "position"
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@ramezgerges
ramezgerges committed May 29, 2024
1 parent 3d6a698 commit 550be6b
Showing 1 changed file with 30 additions and 40 deletions.
70 changes: 30 additions & 40 deletions src/Uno.UI/UI/Xaml/Controls/TextBox/TextBox.skia.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,7 @@ public partial class TextBox

private (int start, int length) _selection;
private bool _selectionEndsAtTheStart;
private float _caretXOffset; // this is not necessarily the visual offset of the caret, but where the caret is logically supposed to be when moving up and down with the keyboard, even if the caret is temporarily elsewhere
private bool _showCaret = true;

private bool _inSelectInternal;
Expand Down Expand Up @@ -327,8 +328,9 @@ partial void SelectPartial(int start, int length)
TrySetCurrentlyTyping(false);
if (!_inSelectInternal)
{
// SelectInternal sets _selectionEndsAtTheStart on its own
// SelectInternal sets _selectionEndsAtTheStart and _caretXOffset on its own
_selectionEndsAtTheStart = false;
_caretXOffset = (float)(DisplayBlockInlines?.GetRectForIndex(start + length).Left ?? 0);
}
_selection = (start, length);
if (!_isSkiaTextBox)
Expand Down Expand Up @@ -492,6 +494,8 @@ partial void OnKeyDownPartial(KeyRoutedEventArgs args)
selectionStart = Math.Max(0, Math.Min(text.Length, selectionStart));
selectionLength = Math.Max(-selectionStart, Math.Min(text.Length - selectionStart, selectionLength));

var caretXOffset = _caretXOffset;

_suppressCurrentlyTyping = true;
if (text == Text)
{
Expand All @@ -508,7 +512,16 @@ partial void OnKeyDownPartial(KeyRoutedEventArgs args)
_clearHistoryOnTextChanged = true;
}
_suppressCurrentlyTyping = false;

// don't change the caret offset when moving up and down
if (args.Key is VirtualKey.Up or VirtualKey.Down)
{
// this condition is accurate in the case of hitting Down on the last line
// or up on the first line. On WinUI, the caret offset won't change.
_caretXOffset = caretXOffset;
}
}

private void KeyDownBack(KeyRoutedEventArgs args, ref string text, bool ctrl, bool shift, ref int selectionStart, ref int selectionLength)
{
if (_isPressed)
Expand Down Expand Up @@ -566,7 +579,7 @@ private void KeyDownUpArrow(KeyRoutedEventArgs args, string text, bool ctrl, boo

var start = selectionStart;
var end = selectionStart + selectionLength;
var newEnd = GetUpResult(text, selectionStart, selectionLength, shift);
var newEnd = GetUpDownResult(text, selectionStart, selectionLength, shift, up: true);
if (shift)
{
selectionLength = newEnd - selectionStart;
Expand Down Expand Up @@ -594,7 +607,7 @@ private void KeyDownDownArrow(KeyRoutedEventArgs args, string text, bool ctrl, b

var start = selectionStart;
var end = selectionStart + selectionLength;
var newEnd = GetDownResult(text, selectionStart, selectionLength, shift);
var newEnd = GetUpDownResult(text, selectionStart, selectionLength, shift, up: false);
if (shift)
{
selectionLength = newEnd - selectionStart;
Expand Down Expand Up @@ -829,6 +842,12 @@ private void SelectInternal(int selectionStart, int selectionLength)
{
_inSelectInternal = true;
_selectionEndsAtTheStart = selectionLength < 0;
if (DisplayBlockInlines is { }) // this check is important because on start up, the Inlines haven't been created yet.
{
_caretXOffset = selectionLength >= 0 ?
(float)DisplayBlockInlines.GetRectForIndex(selectionStart + selectionLength).Left :
(float)DisplayBlockInlines.GetRectForIndex(selectionStart + selectionLength).Right;
}
Select(Math.Min(selectionStart, selectionStart + selectionLength), Math.Abs(selectionLength));
_inSelectInternal = false;
}
Expand Down Expand Up @@ -1038,9 +1057,9 @@ protected override void OnDoubleTapped(DoubleTappedRoutedEventArgs args)
/// <summary>
/// There are 2 concepts of a "line", there's a line that ends at end-of-text, \r, \n, etc.
/// and then there's an actual rendered line that may end due to wrapping and not a line break.
/// GetUpResult and GetDownResult care about the second kind of lines.
/// This method cares about the second kind of lines.
/// </summary>
private int GetUpResult(string text, int selectionStart, int selectionLength, bool shift)
private int GetUpDownResult(string text, int selectionStart, int selectionLength, bool shift, bool up)
{
if (text.Length == 0)
{
Expand All @@ -1052,50 +1071,21 @@ private int GetUpResult(string text, int selectionStart, int selectionLength, bo
var startLineIndex = lines.IndexOf(startLine);
var endLineIndex = lines.IndexOf(endLine);

if (shift && endLineIndex == 0)
if (up && shift && endLineIndex == 0)
{
return 0; // first line, goes to the beginning
}

var newLineIndex = selectionLength < 0 || shift ? Math.Max(0, endLineIndex - 1) : Math.Max(0, startLineIndex - 1);

var rect = DisplayBlockInlines.GetRectForIndex(selectionStart + selectionLength);
var x = shift && selectionLength > 0 ? rect.Right : rect.Left;
var y = (newLineIndex + 0.5) * rect.Height; // 0.5 is to get the center of the line, rect.Height is line height
var index = Math.Max(0, DisplayBlockInlines.GetIndexAt(new Point(x, y), true, true));
if (text.Length > index - 1
&& index - 1 >= 0
&& index == lines[newLineIndex].start + lines[newLineIndex].length
&& (text[index - 1] == '\r' || text[index - 1] == ' '))
{
// if we're past \r or space, we will actually be at the beginning of the next line, so we take a step back
index--;
}

return index;
}

private int GetDownResult(string text, int selectionStart, int selectionLength, bool shift)
{
if (text.Length == 0)
{
return 0;
}
var startLine = GetLineAt(text, selectionStart, 0);
var endLine = GetLineAt(text, selectionStart + selectionLength, 0);
var lines = DisplayBlockInlines.GetLineIntervals();
var startLineIndex = lines.IndexOf(startLine);
var endLineIndex = lines.IndexOf(endLine);

if (!shift && (startLineIndex == lines.Count - 1 || endLineIndex == lines.Count - 1))
else if (!up && !shift && (startLineIndex == lines.Count - 1 || endLineIndex == lines.Count - 1))
{
return text.Length; // last line, goes to the end
}

var newLineIndex = selectionLength > 0 || shift ? Math.Min(lines.Count, endLineIndex + 1) : Math.Min(lines.Count, startLineIndex + 1);
var newLineIndex = up ?
selectionLength < 0 || shift ? Math.Max(0, endLineIndex - 1) : Math.Max(0, startLineIndex - 1) :
selectionLength > 0 || shift ? Math.Min(lines.Count, endLineIndex + 1) : Math.Min(lines.Count, startLineIndex + 1);

var rect = DisplayBlockInlines.GetRectForIndex(selectionStart + selectionLength);
var x = shift && selectionLength > 0 ? rect.Right : rect.Left;
var x = _caretXOffset;
var y = (newLineIndex + 0.5) * rect.Height; // 0.5 is to get the center of the line, rect.Height is line height
var index = Math.Max(0, DisplayBlockInlines.GetIndexAt(new Point(x, y), true, true));
if (text.Length > index - 1
Expand Down

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