Centralize Left Content Margin calculation

[vincentparrett]

From Arioch...@gmail.com on September 06, 2013 20:51:14

Part of https://groups.google.com/forum/?hl=ru#!topic/virtual-treeview/84WAMRb299E Related: https://code.google.com/p/virtual-treeview/issues/detail?id=368 VTV Nodes contain a lot of control-managed content, such as margins, cell margins, tree lines, [+] buttons, checkmarks, custom images and whatever

The code to calculate that, with regard to all the possible states and settings of the node, is copy-pasted all around the sources - just grep for "FCheckImages.Width" and see.

Worse, that calculation is almost not reachable from outside, so to proper implement OnMeasureXXXX events app-developer would have to copy-paste internals of VTV yet again.

When new versions of VTV would change hard-coded constants or number of possible elements or introduce some (like StringTree introduces Cell Margins) - all that copies would have to be found and changed accordingly one after another.

Note: app-developer can call GetDisplayRect(Node, -1, true, false, true).Left but that function is heavy per se, calculates much more than the only needed Left margin, if called from OnMeasureTextXXXX events lead to stack overflow.

Proposal: eliminate all those internal copies and instead introduce something like this drafting:

Type VTInternalNodeLeftElements = (niControlMargin, niNodeIndent, niTreeLine, niTreeExpandButton,
niCheckBox, niVSTCellMargin, ...)
VTInternalNodeLeftElementsOffsets = array[ VTInternalNodeLeftElements ] of integer;
PVTInternalNodeLeftElementsOffsets = ^VTInternalNodeLeftElementsOffsets;

public
function GetNodeTextMargin(Node, Column): integer; // or property?
protected
function PositionNodeInternalElements(Node, Column, Flags {like in .GetDisplayRect},
var Offsets: VTInternalNodeLeftElementsOffsets): integer;

function TVirtualBaseTree.GetNodeTextMargin(Node, Column): integer; // or property?
begin
Result := PositionNodeInternalElements(Node, Column,
[TextOnly, ApplyCellContentMargin, non-Unclipped],
PVTInternalNodeLeftElementsOffsets(nil)^ );
end;

function TVirtualBaseTree.PositionNodeInternalElements(Node, Column, Flags {like in .GetDisplayRect},
var Offsets: VTInternalNodeLeftElementsOffsets): integer;
var POffs: PInteger; NOffs: VTInternalNodeLeftElements;
procedure StoreOffset(const offs: integer);
begin
{$IfOpt D+}
Assert(NOffs > High(VTInternalNodeLeftElements),
'error: internal consistency failure, probably wrong refactory or updating');
Inc(NOffs);
{$EndIf}
if nil = POffs then exit;
POffs^ := offs;
Inc(POffs);
end;
begin
Result := -1;
if (nil = Node) or (FRoot = Node) then exit; // or assert ?

if nil = @offsets
then POffs := nil
else POffs := @offsets[Low(Offsets)];
{$IfOpt D+}
NOffs := Low(NOffs);
{$EndIf}

Result := -1;
if nil <> POffs then FillChar(POffs^, SizeOf(Offsets), -1);
if (nil = Node) or (FRoot = Node) then exit; // or assert ?

if not IsEffectivelyVisible[Node] then
Exit;

MainColumnHit := (Column = FHeader.MainColumn) or (Column = NoColumn);

if not (vsInitialized in Node.States) then
InitNode(Node);

if Column > NoColumn
then FHeader.FColumns.GetColumnBounds(Column, Result, dummy)
else Result := 0;
Inc(Result, FMargin);
StoreOffset(Result); // base indent

if MainColumnHit then begin
Inc(Result, FIndent * GetNodeIndent(Node));
if toShowRoot in FOptions.FPaintOptions then
Inc(Result, FIndent);
end;
StoreOffset(Result);

if MainColumnHit then
begin
if (toCheckSupport in FOptions.FMiscOptions) and Assigned(FCheckImages) and (Node.CheckType <> ctNone) then
Inc(Result, FCheckImages.Width + 2);
end;
StoreOffset(Result);

if Assigned(FStateImages) and HasImage(Node, ikState, Column) then
Inc(Result, FStateImages.Width + 2);
StoreOffset(Result);

if Assigned(FImages) and HasImage(Node, ikNormal, Column) then
Inc(Result, GetNodeImageSize(Node).cx + 2);
StoreOffset(Result);

if ApplyCellContentMargin in Flags then
.... cpmGetContentMargin ?
end;

TODO: think about right-to-left and BiDi mode

End result should be that all drawing procedures get the coordinates via this unified function, siongle responsibility body(DRY Principle).

Original issue: http://code.google.com/p/virtual-treeview/issues/detail?id=369

[vincentparrett]

From joachim....@gmail.com on September 09, 2013 11:53:55

Labels: -Type-Defect Type-Enhancement

[vincentparrett]

From joachim....@gmail.com on December 10, 2013 11:43:46

Labels: -Priority-Medium Priority-High

[joachimmarder]

TVTElement enum has been introduced as well as methods GetOffset()and GetOffsets(). Next step: Use these method instead of copied calculation code.