在 TCornerButton 的画布上绘图时位置错误

Question

我创建了一个继承自 TCornerButton 的新组件来添加下拉菜单选项。

第一个问题...

为什么我需要重写“AfterPaint”方法而不是文档中描述的“Paint”方法。覆盖“Paint”也不会导致任何绘图。

第二个问题...

当我使用“AfterPaint”方法绘制一个向下的小箭头时，其向右偏移约 5 个像素，直到按钮获得焦点。仅将鼠标悬停在按钮上似乎并不能解决问题（正如您期望发生的重新绘制一样）。我已经将其与代码中的“ScalePoint”和没有“ScalePoint”联系起来，但每次都是错误的。 它还在设计时显示在错误的位置。一旦按钮在运行时获得焦点，箭头就会移动到预期位置。当它失去焦点时，它会移回到错误的位置。 供参考。 “宽度”没有改变 - 我已经对此进行了测试。

procedure TLFButton.AfterPaint;
var
  down_arrow: TPolygon;
  x, y: Extended;
begin
  inherited;
  if FDropDownButton then
  begin
    Canvas.Fill := TText(FindStyleResource('text')).Fill;
    x := Width - 12;
    y := (Height / 2) - 3;
    SetLength(down_arrow, 3);
    down_arrow[0] := ScalePoint(PointF(x, y), Scale.X, Scale.Y);
    down_arrow[1] := ScalePoint(PointF(x+8,y), Scale.X, Scale.Y);
    down_arrow[2] := ScalePoint(PointF(x+4,y+6), Scale.X, Scale.Y);
    Canvas.FillPolygon(down_arrow, 255);
  end;
end;

Answer 1

另一种方法是使用 StyleLookup。
通过使用 StyleLookup，设计人员可以在不更改代码的情况下更改向下箭头。

constructor TLFButton.Create(AOwner: TComponent);
begin
  inherited;
  FDropDownButton := true;
end;

procedure TLFButton.SetDropDownButton(const Value: boolean);
var
  obj: TFmxObject;
begin
  FDropDownButton := Value;
  obj := FindStyleResource('dropdownbutton');
  if obj is TControl then
    TControl(obj).visible := Value;
end;

将下面的代码保存在 LFButton.Style 文本文件中并将其加载到样本中。
TPath = 向下的小箭头。

object _1: TLayout
  Align = alClient
  Position.Point = '(0,33)'
  Width = 842.000000000000000000
  Height = 715.000000000000000000
  object TLayout
    StyleName = 'LFButtonStyle'
    Position.Point = '(375,345)'
    Width = 91.000000000000000000
    Height = 24.000000000000000000
    DesignVisible = False
    object TRectangle
      StyleName = 'background'
      Align = alContents
      Width = 91.000000000000000000
      Height = 24.000000000000000000
      HitTest = False
      Fill.Kind = bkGradient
      Fill.Gradient.Points = <
        item
          Color = claWhite
        end
        item
          Color = xFFFEFEFE
          Offset = 0.472727268934249900
        end
        item
          Color = xFFDDDDDD
          Offset = 0.512727260589599600
        end
        item
          Color = xFFDBDBDB
          Offset = 1.000000000000000000
        end>
      Stroke.Color = xFF989898
      XRadius = 3.000000000000000000
      YRadius = 3.000000000000000000
      object TGradientAnimation
        Duration = 0.200000002980232200
        Trigger = 'IsMouseOver=true;IsPressed=false'
        StartValue.Points = <
          item
            Color = claWhite
          end
          item
            Color = xFFFEFEFE
            Offset = 0.472727268934249900
          end
          item
            Color = xFFDDDDDD
            Offset = 0.512727260589599600
          end
          item
            Color = xFFDBDBDB
            Offset = 1.000000000000000000
          end>
        StopValue.Points = <
          item
            Color = xFFA5D9FF
          end
          item
            Color = xFFA5D9FF
            Offset = 0.472727268934249900
          end
          item
            Color = xFFA5D9FF
            Offset = 0.512727260589599600
          end
          item
            Color = xFFA5D9FF
            Offset = 1.000000000000000000
          end>
        PropertyName = 'Fill.Gradient'
      end
      object TGradientAnimation
        Duration = 0.200000002980232200
        Trigger = 'IsMouseOver=false;IsPressed=false'
        StartValue.Points = <
          item
            Color = xFFA5D9FF
          end
          item
            Color = xFFA5D9FF
            Offset = 0.472727268934249900
          end
          item
            Color = xFFA5D9FF
            Offset = 0.512727260589599600
          end
          item
            Color = xFFA5D9FF
            Offset = 1.000000000000000000
          end>
        StopValue.Points = <
          item
            Color = claWhite
          end
          item
            Color = xFFFEFEFE
            Offset = 0.472727268934249900
          end
          item
            Color = xFFDDDDDD
            Offset = 0.512727260589599600
          end
          item
            Color = xFFDBDBDB
            Offset = 1.000000000000000000
          end>
        PropertyName = 'Fill.Gradient'
      end
      object TColorAnimation
        Duration = 0.200000002980232200
        Inverse = True
        Trigger = 'IsMouseOver=false;IsPressed=true'
        StartValue = xFF34BFFE
        StopValue = xFFA5D9FF
        PropertyName = 'Fill.Color'
      end
      object TColorAnimation
        Duration = 0.200000002980232200
        Trigger = 'IsMouseOver=true;IsPressed=true'
        StartValue = xFF34BFFE
        StopValue = xFFA5D9FF
        PropertyName = 'Fill.Color'
      end
    end
    object TText
      StyleName = 'text'
      Align = alClient
      Position.Point = '(5,3)'
      Locked = True
      Width = 66.000000000000000000
      Height = 18.000000000000000000
      Padding.Rect = '(5,3,5,3)'
      HitTest = False
      Text = 'button'
    end
    object TGlowEffect
      Trigger = 'IsFocused=true'
      Enabled = False
      Softness = 0.200000002980232200
      GlowColor = x82005ACC
      Opacity = 0.899999976158142100
    end
    object TLayout
      Align = alRight
      Position.Point = '(76,0)'
      Locked = True
      Width = 15.000000000000000000
      Height = 24.000000000000000000
      object TPath
        StyleName = 'dropdownbutton'
        Align = alCenter
        Position.Point = '(3,9)'
        Width = 8.000000000000000000
        Height = 5.000000000000000000
        HitTest = False
        Fill.Color = claBlack
        Stroke.Kind = bkNone
        Data.Path = {
          04000000000000000000000000000000010000000000803F0000000001000000
          0000003F0000803F030000000000000000000000}
      end
    end
  end
end