我一直在努力寻找一种方法来找到a的可见/可见宽度 非常宽的列，基于底层字段的长度。
在运行时查看网格时，通常会运行列的数据之一 屏幕右侧。要查看您必须滚动的数据 在右边。不幸的是，UI设计不适合显示 单独的备忘录字段。
我所做的是使用JEDI项目中的TJvBalloonHint 与TJvDBGrid结合使用。使用网格的OnShowCellHint我调用了一个 自定义方法，用于构建提示文本，计算显示位置 提示并显示它。
******TJvDBGrid descendant*******
procedure TMyJvDBGrid.ShowGridCellHint(Sender: TObject; Field: TField;
var AHint: String; var ATimeOut: Integer);
begin
FBalloonHint.HintPos(ScreenToClient(Mouse.CursorPos).X,ScreenToClient(Mouse.CursorPos).Y);
end;
********************************
function GetTextWidth(const Text: UnicodeString; AFont: TFont): Integer;
var
bmp: Vcl.Graphics.TBitmap;
begin
bmp := Vcl.Graphics.TBitmap.Create;
try
bmp.Canvas.Font := AFont;
Result := bmp.Canvas.TextWidth(Text);
finally
FreeAndNil(bmp);
end;
end;
******TJvBalloonHint descendant*******
procedure TMyJvBalloonHint.HintPos(X, Y: Integer);
var
Cell: TGridCoord;
ActRec: Integer;
r: TRect;
Grid: TMyJvDBGrid;
sTitle: UnicodeString;
begin
Grid := TMyJvDBGrid(Self.Owner);
// correlates pixel location of the mouse
// cursor to the row & column in the grid
Cell := Grid.MouseCoord(X, Y);
if dgIndicator in Grid.Options then
// indicator column counts as a column
Dec(Cell.X);
if dgTitles in Grid.Options then
// titles counts as a row
Dec(Cell.Y);
// is the grid connected to a dataset via a TDataSource object?
if Grid.DataLink.Active and (Cell.X >= 0) and (Cell.Y >= 0) then
begin
// preserve the active record
ActRec := Grid.DataLink.ActiveRecord;
try
// set active record to the row under the mouse cursor
Grid.DataLink.ActiveRecord := Cell.Y;
// set hint to the field value under the mouse cursor
Hint := Grid.Columns[Cell.X].Field.AsString;
// set hint title to the name of the column under the mouse cursor
sTitle := Grid.Columns[Cell.X].Field.FieldName;
if CellChanged(Cell.X,Cell.Y) then
if GetTextWidth(Hint,Grid.Font) > Grid.Width then
begin
r.TopLeft := Point(mouse.CursorPos.X,Mouse.CursorPos.Y);
r.BottomRight := Point(mouse.CursorPos.X,Mouse.CursorPos.Y);
Grid.BalloonHint.ActivateHintRect(r,sTitle,Hint,0,ikNone);
end;
finally
Grid.DataLink.ActiveRecord := ActRec;
end;
end;
end;
function TMyJvBalloonHint.CellChanged(const X, Y: Integer): Boolean;
var
Grid: TMyJvDBGrid;
begin
// persists cell position in order to determine if the
// mouse cursor position has changed to another cell
Result := False;
if (X <> FX) or (Y <> FY) then
begin
Grid := TMyJvDBGrid(Self.Owner);
if Grid.BalloonHint.Active then
Grid.BalloonHint.CancelHint;
Result := True;
if Assigned(FOnShowHint) and FShowHint then
FOnShowHint(Self);
FX := X;
FY := Y;
end;
end;
procedure TMyJvBalloonHint.SetHint(AValue: UnicodeString);
var
i,n: Integer;
chars: TSysCharSet;
begin
FHint := '';
chars := [];
if Length(TextWrapChars.Chars) > 0 then
begin
for i := 0 to Pred(Length(TextWrapChars.Chars)) do
for n := 1 to Length(TextWrapChars[i]) do
if TextWrapChars[i] <> #0 then
Include(chars,TextWrapChars[i]);
FHint := WrapText(AValue, #13#10, chars, TextWrapWidth);
end
else
FHint := AValue;
end;
**************************************
此代码仅显示提示 - 包含字段的文本 它是完整的 - 如果字段文本长于 整个网格的显示宽度。
第1问：） 我想要做的是仅在字段文本更大时显示提示 长度大于列的显示/可见宽度。但我不能 找到一种方法来测量列的显示/可见宽度。其他 如果一列比它显示的宽度宽，我想知道 列的显示/可见部分的宽度是多少。然后我 可以测量基础字段中文本的宽度并确定 如果文本在网格的右侧或左侧被切断。
第二季Q）： 上面的代码显示了光标位置的提示。我想 在单元格的可见部分底部显示提示 无论光标在哪里，单元格可见部分的中心 在细胞直肠内横向。
感谢您的帮助。
答案 0 :(得分：1)
这并不完美，但它很接近于回答这两个问题。
由于我将TDBGrid子类化，因此我可以访问受保护的成员，包括'LeftCol'。使用网格的'ClientWidth'属性和对列的迭代，我能够粗略计算'切断'列的起始位置，并使用此方法显示/可见宽度：
function ColumnIsChopped(Grid: TIniSectionDBGrid; const ColNum: Integer;
out ColumnDisplayWidth, ColumnLeftPos: Integer): Boolean;
var
i: Integer;
begin
if ColNum > Pred(Grid.Columns.Count) then
Exit;
// the whole enchilada...
ColumnDisplayWidth := Grid.ClientWidth;
if ColNum <> Grid.LeftCol then
begin
// start iteration & measurements with the left most displayed column in grid
i := Grid.LeftCol;
while i < ColNum do
begin
// subtract width of column from overall grid client (displayed) width
ColumnDisplayWidth := ColumnDisplayWidth - Grid.Columns[i].Width;
inc(i);
end;
end;
// determine the starting position in pixels of the provided column
ColumnLeftPos := Grid.ClientWidth - ColumnDisplayWidth;
// if remaining display width is less than the text width of text in column,
// assume that the column text display is chopped off on the right
Result := ColumnDisplayWidth <= GetTextWidth(Grid.Columns[ColNum].Field.AsString,Grid.Font);
end;
在准备显示提示时，我调用ColumnIsChopped方法来确定以下内容：
procedure TIniSectionDBGrid.TIniSectionDBGridHint.HintPos(Position: TPoint);
var
Cell: TGridCoord;
ActRec,colDisplayWidth,iLeft,iLeftPos: Integer;
r: TRect;
Grid: TIniSectionDBGrid;
sTitle: UnicodeString;
begin
Grid := TIniSectionDBGrid(Self.Owner);
// correlates pixel location of the mouse
// cursor to the row & column in the grid
Cell := Grid.MouseCoord(Position.X, Position.Y);
if dgIndicator in Grid.Options then
// indicator column counts as a column
Dec(Cell.X);
if dgTitles in Grid.Options then
// titles counts as a row
Dec(Cell.Y);
// is the grid connected to a dataset via a TDataSource object?
if Grid.DataLink.Active and (Cell.X >= 0) and (Cell.Y >= 0) then
begin
// preserve the active record
ActRec := Grid.DataLink.ActiveRecord;
try
// set active record to the row under the mouse cursor
Grid.DataLink.ActiveRecord := Cell.Y;
if CellChanged(Cell.X,Cell.Y) then
if ColumnIsChopped(Grid,Cell.X,colDisplayWidth,iLeft) then
begin
// calc x position for hint
iLeftPos := iLeft + Round(colDisplayWidth / 2);
// set hint to the field value under the mouse cursor
Hint := Grid.Columns[Cell.X].Field.AsString;
// set hint title to the name of the column under the mouse cursor
sTitle := Grid.Columns[Cell.X].Field.FieldName;
r.TopLeft := Point(iLeftPos,Mouse.CursorPos.Y);
r.BottomRight := Point(iLeftPos,Mouse.CursorPos.Y);
Grid.BalloonHint.ActivateHintRect(r,sTitle,Hint,0,ikNone);
end;
finally
Grid.DataLink.ActiveRecord := ActRec;
end;
end;
end;
现在剩下的就是弄清楚如何将提示定位在单元格的底部或单元格的顶部，具体取决于单元格在网格中的垂直方向以及与单元格相关的相应提示方向（上面或以下？）。