How can my Delphi component detect at design time if any other component is being dropped on the form?
You should override Notification method of your component; something like that:
type
TMyComponent = class(TComponent)
//..
protected
procedure Notification(AComponent: TComponent;
Operation: TOperation); override;
end;
procedure TMyComponent.Notification(AComponent: TComponent;
Operation: TOperation);
begin
inherited Notification(AComponent, Operation);
if (Operation = opInsert) and (csDesigning in ComponentState) then begin
// AComponent was dropped on the form
end;
end;
If you mean controls being dropped instead of components, and if you mean dropping on your component rather than dropping on the form, then:
Add an CM_CONTROLLISTCHANGE message handler to track controls before they are inserted, or
Add an CM_CONTROLCHANGE message handler to track controls after they are inserted (WParam points to the control),
Don't do this until csLoading is out of ComponentState to prevent tracking during form creation by the IDE.
Just a tip, if it helps... i am having a similar issue:
I want to hide non-visual component icon (for my TMyLabel=class(Classes.TComponent) component) when i drop it from IDE inside a Form, Panel, etc ...
I have oveloaded: Loaded and ReadState to get such icon out of sight (at design-time) ... on Loaded & ReadState i put DesignInfo to point to (-100,-100), so icon is not shown
I have oveloaded: WriteState to avoid Left & Top be saved to the .dfm (at design-time) ... on WriteState i put it to point (0,0), so it is not saved inside the .dfm
Note: I use same technique/trick to not save properties i do not want, etc ... i really only let Caption to be saved inside the .dfm
The question / tip is:
When i drop a new "control" (of my component) into the form, such icon is visible just where i drop it... how to hide it?
Maybe user1580348 is trying something similar ... or something related to auto-align such non-visual "controls" / "components".
In other words:
How can we control the icon position when dropping a new (our component) control on a form, panel, etc...
I know my problem is much easier, but i did not yet solve it... i want just to hide that icon IDE shows for non-visual components (only for controls that are of my component)... but maybe knowing how to it will also helps user1580348.
As i said, it is just a tip/clue.
Related
i have a problem with the VCL-Styles and MDI-Form. I want to use the VCL Styles, but i also want to draw the background (image) of my MainForm (MDI) by myself. This worked fine without VCL Styles, but when a Style is active the background image of the MainForm isn't shown.
I checked out the StyleElements for the MainForm, but exclude the seClient is ignoerd and the background image isn't shown.
When i exclude the seClient and seBoarder the image is shown again. Obviously the Form Boarder lost the Style, which is also not that what i want.
The image is drawn at the Canvas in the ClientWndProc by the messages WM_ERASEBKGND, WM_VSCROLL and WM_HSCROLL. With the Styles, it looks like this events didn't raise. Is there any way the get the image at the form background with VCL Styles active?
The main point to realize here is that form styled fsMDIForm is a very special TWinControl that manages two window handles instead of one - TWinControl.Handle and TForm.ClientHandle. While the first handle is the form window itself the second is MDI client window (container-like for MDI child windows inside MDI parent).
TFormStyleHook hooks both window procedures and introduces new method TFormStyleHook.MDIClientWndProc, which processes messages sent to MDI client. This method luckily virtual. It does some pre-processing of messages and then calls the original hooked procedure. The sad part is that it prevents calling the old procedure for WM_NCACTIVATE, WM_NCCALCSIZE, WM_NCPAINT and WM_ERASEBKGND. Even worse is that on WM_ERASEBKGND it paints the client area background directly using StyleServices.
Thanks to the above the subclassing of TFormStyleHook for MDI forms a PITA. I see multiple design flaws here:
Missing virtual TFormStyleHook.PaintMDIClientBackground similar to TFormStyleHook.PaintBackground.
No way to control/access over the original MDI client proc without hacking (hidden in private field FMDIPrevClientProc).
Disability to control styling of MDI client window via TForm.StyleElements (as noted by OP).
So what is the workaround? The easiest I can see is creating a custom style hook:
type
TMainFormStyleHook = class(TFormStyleHook)
public
procedure MDIClientWndProc(var Message: TMessage); override;
end;
{ TMainFormStyleHook }
procedure TMainFormStyleHook.MDIClientWndProc(var Message: TMessage);
begin
if Message.Msg = WM_ERASEBKGND then
begin
{ TODO: Paint background to TWMEraseBkgnd(Message).DC }
Message.Result := 1;
end
else
inherited;
end;
and applying it to your MDI parent:
type
TMainForm = class(TForm)
private
class constructor Create;
class destructor Destroy;
{ ... }
end;
{ TMainForm }
class constructor TMainForm.Create;
begin
TCustomStyleEngine.RegisterStyleHook(TMainForm, TMainFormStyleHook);
end;
class destructor TMainForm.Destroy;
begin
TCustomStyleEngine.UnRegisterStyleHook(TMainForm, TMainFormStyleHook);
end;
Note that you still need to keep painting background in MDI parent form in case the VCL styles are disabled, so it's worth creating method TMainForm.PaintMDICLientBackground(DC: HDC) and call it from both places.
I would argue that this is a bug in VCL. How about you guys?
I would like to change the property visible of a component when I select it in the structure panel. I know for example that when I select a component in the structure panel then the parent of my component will receive 2 new objects (to draw the selection, maybe), TGrabHandle.TGrabHandleEllipse and TDesignRectangle
So I can detect that I select a component in the structure panel by overriding the DoAddObject procedure of the parent of my control like this :
procedure TMyControl.DoAddObject(const AObject: TFmxObject);
begin
if (csDesigning in ComponentState) and
(AObject.ClassNameIs('TGrabHandle.TGrabHandleEllipse')) or
(AObject.ClassNameIs('TDesignRectangle')) then begin
....
end
end;
But all of this seems to be a little complicated and I would like to know if there is a better way to know (at design time) when a component is selected in the structure panel?
I have my own Treeview control derived from TCustomTreeView.
I have added some of my own procedures to the class such as adding nodes. When this procedure is called at runtime I wanted the newly added node to be selected and for the Treeview to be focused so the new node is highlighted.
Here is a extract:
procedure TMyTreeView.AddGroup(AName: string);
var
Node: TTreeNode;
Obj: TGroup;
procedure AddToTree;
begin
Obj := TGroup.Create(AName);
FGroups.Add(Obj);
Node := Items.AddObject(Node, AName, Obj);
with Node do
begin
ImageIndex := 0;
SelectedIndex := 0;
end;
Selected := Node;
SetFocus;
end;
begin
Node := nil;
AddToTree;
end;
The above works but I am facing the common error message when calling from the Forms OnCreate event:
Cannot focus a disabled or invisible window
I know you can use the OnActivate event or just don't use OnCreate at all which will not result in the error, but anyone else who may use the component may not realise this.
So I wanted to know if there is a way to determine if my Treeview (or any control) is able to receive the focus, then I could add a little checking of my own, something like:
if ControlIsFocusable then
begin
Selected := Node;
SetFocus;
end;
I know there is the Loaded procedure you can override which tells us when the control is loaded but then that would only work on first run. If the control became hidden by the user at runtime (or was not visible to begin with) the Cannot focus a disabled or invisible window error is still going to show up.
The dirty way to do it when not run in the debugger is:
try
Selected := Node;
SetFocus;
except
end;
But that defeats the purpose and I hate handling errors in this way.
So basically I wanted to know if there was a way to determine if a control can receive focus, so that we can set the focus to it?
I'm not going to answer the question that you asked, because I think you are doing this wrong.
The control should not call SetFocus on itself. I can imagine no scenario where that is the correct behaviour. The form or application or framework should determine focus. Not the control.
Imagine what happens when you have a form with two such controls? Imagine using the keyboard to focus a button, which you then press with the SPACE bar. If the action attached to the button calls your control's method which then changes the focus, you've just gone against the platform UI guidelines. You control now places a severe burden on any application that attempts to consume it.
When Delphi (2006) goes quantum: I've got "something" that appears to be both a TToolBar and a TPanel, depending on how you observe it. I'd like to understand what's going on.
Here is how to create it and what happens:
in the DFM
add a TToolBar named bar;
in that TToolBar, put a TPanel.
in the code and at runtime:
the panel appears in the list of buttons bar.Buttons[], let's say at index i
bar.Buttons[i], from the compiler point of view, is a TToolButton
bar.Buttons[i].ClassName = 'TPanel'
(bar.Buttons[i] is TToolButton) = true, but that's the compiler optimising the call to 'is' out;
indeed IsBarButton(bar.Buttons[i]) is false for function IsBarButton (defined below);
bar.Buttons[i].Name is the name I gave the TPanel in the DFM
inspecting the value bar.Buttons[i] in the debugging:
it has a property 'Caption' the real TToolButton's don't have
strangely, it has all properties TToolButton's have, like TToolButton.Indeterminate (=true).
IsToolButton:
function IsToolButton(X : TObject) : boolean;
begin
Result := X is TToolButton;
end;
So bar.Buttons[i] both is and is not a TToolButton... what's up ?
(Bottom story is I'd like to distinguish my TPanel from the genuine TToolButton's. This I can do in more or less hackish ways. My goal by asking this question here, is to get a fuller understanding of what's really happening here.)
Question: what is happening ?
Sub-question: is it legitimate to add a TPanel to a TToolBar ?
The only thing the OS allows to be added to a tool bar is a tool button. To add anything else, you technically need to create a button and then put your other things on top of it. The button that gets added is literally a placeholder. It's there to take up space so the next thing you add gets positioned properly.
You can see this sometimes if the non-tool-button control you add is transparent. Then you can see the tool bar's separator underneath, so it looks like there's a vertical line running through the middle of your control.
When you add a non-tool-button control to the tool bar, the Buttons property indeed lies about the type of the control. You'll notice throughout ComCtrls.pas that TToolBar itself always casts the buttons to TControl and then checks whether they really descend from TToolButton. It's completely legitimate to add non-buttons to a tool bar; that's why the Form Designer allows it in the first place.
I suggest you use the Form Designer to create your tool bar. That way, the IDE will maintain an identifier for you in your form, so you'll always have a direct reference to your panel. You won't have to go hunting for it in the tool bar. Even if you're creating the tool bar manually, it's a good idea to make an extra field to refer to the panel. Even if you move the panel around within the tool bar, it will still be the same object the whole time, so you needn't worry about dangling references.
When you put a couple of buttons and a panel on a toolbar, and a Memo somewhere, then run this code in the form's onCreate:
procedure TForm1.FormCreate(Sender: TObject);
function _IsToolButton(const aObject: TObject): Boolean;
begin
Result := aObject is TToolButton;
end;
function _IsPanel(const aObject: TObject): Boolean;
begin
Result := aObject is TPanel;
end;
var
i: Integer;
begin
for i := 0 to bar.ButtonCount - 1 do begin
Memo.Lines.Add(Format('bar.Buttons[%d].Name: %s', [i, bar.Buttons[i].Name]));
Memo.Lines.Add(Format('bar.Buttons[%d].ClassName: %s', [i, bar.Buttons[i].ClassName]));
Memo.Lines.Add(Format('bar.Buttons[%d] is TToolButton: %s', [i, BoolToStr(_IsToolButton(bar.Buttons[i]), True)]));
Memo.Lines.Add(Format('bar.Buttons[%d] is TPanel: %s', [i, BoolToStr(_IsPanel(bar.Buttons[i]), True)]));
// Memo.Lines.Add(Format('bar.Buttons[%d] has Caption property: %s', [i, 'dunno yet']));
Memo.Lines.Add('');
end;
end;
you'll see that the panel is not a TooButton and most definitely a TPanel.
The debugger showing properties of a ToolButton for the panel, is simply the debugger casting each and every bar.Buttons[i] to a TToolButton. When you right-click on the "Data" tab of the Debug inspector, you can Type Cast it to a TPanel and you will get the correct information.
'is it legitimate?' - well, you are definitely using the toolbar in a way that the creator of the toolbar did not ment it to be used. Will it blow up in your face? Who knows. I guess you could walk through the sourcecode for the toolbar and check if it is safe or not, but what about possible third party tools or components, expecting to find buttons in a toolbar?
I would see if I could find another way of solving my problem. Clever hacks have a tendency to turn out not so clever after all, and it will surely higten the wtf-rate of your code.
Do you have to use a toolbar? What about a flowpanel with buttons and panels instead? Or a panel with a toolbar and a panel?
I don't know whether this question can be answered here, but I hope it will.
I wrote a simple text editor in Delphi 7 that serves as my primary IDE for writing C code under Windows. I run Windows in a VM and I needed something light.
In any case, it uses a TpageControl that gets a new tab whenever you open or create a new file. Pretty standard.
Now, the TPageControl under Delphi has no flat property.
NO I don't mean setting the tab style to tsButtons or tsFlatButtons
the borders cannot be set to "none" and it looks pretty bad when you add a text editor into the tab control.
Is there any way to make a TpageControl flat?
EDIT:
On an open source PageControl that supports flat here's what I found:
procedure TCustomTabExtControl.WndProc(var Message: TMessage);
begin
if(Message.Msg=TCM_ADJUSTRECT) and (FFlat) then
begin
Inherited WndProc(Message);
Case TAbPosition of
tpTop : begin
PRect(Message.LParam)^.Left:=0;
PRect(Message.LParam)^.Right:=ClientWidth;
PRect(Message.LParam)^.Top:=PRect(Message.LParam)^.Top-4;
PRect(Message.LParam)^.Bottom:=ClientHeight;
end;
tpLeft : begin
PRect(Message.LParam)^.Top:=0;
PRect(Message.LParam)^.Right:=ClientWidth;
PRect(Message.LParam)^.Left:=PRect(Message.LParam)^.Left-4;
PRect(Message.LParam)^.Bottom:=ClientHeight;
end;
tpBottom : begin
PRect(Message.LParam)^.Left:=0;
PRect(Message.LParam)^.Right:=ClientWidth;
PRect(Message.LParam)^.Bottom:=PRect(Message.LParam)^.Bottom-4;
PRect(Message.LParam)^.Top:=0;
end;
tpRight : begin
PRect(Message.LParam)^.Top:=0;
PRect(Message.LParam)^.Left:=0;
PRect(Message.LParam)^.Right:=PRect(Message.LParam)^.Right-4;
PRect(Message.LParam)^.Bottom:=ClientHeight;
end;
end;
end else Inherited WndProc(Message);
end;
The thing is when I tried something similar on the main application it won't work. It won't even compile.
When the tabs are drawn as buttons, no border is drawn around the display area, so set the Style property to tsButtons or tsFlatButtons. (For non-VCL programmers, this is equivalent to including the tcs_Buttons window style on the tab control.)
An alternative is to use a TNotebook. It holds pages, but it doesn't do any painting at all. You'd have to provide the tabs yourself, such as by setting the tab control's height equal to the height of the tabs, or by using a TTabSet. (TTabSet is available in Delphi 2005; I'm not sure about Delphi 7.)
Regarding the code you found, it would be helpful if you indicated why it doesn't compile, or if you gave a link to where you found it, since I suppose the compilation error was because it refers to fields or properties of the custom class rather than the stock one. Here's what you can try to put it in your own code, without having to write a custom control.
Make two new declarations in your form like this:
FOldTabProc: TWndMethod;
procedure TabWndProc(var Msg: TMessage);
In the form's OnCreate event handler, assign that method to the page control's WindowProc property:
FOldTabProc := PageControl1.WindowProc;
PageControl1.WindowProc := TabWndProc;
Now implement that method and handle the tcm_AdjustRect messsage:
procedure TForm1.TabWndProc(var Msg: TMessage);
begin
FOldTabProc(Msg);
if Msg.Msg = tcm_AdjustRect then begin
case PageControl1.TabPosition of
tpTop: begin
PRect(Msg.LParam)^.Left := 0;
PRect(Msg.LParam)^.Right := PageControl1.ClientWidth;
Dec(PRect(Msg.LParam)^.Top, 4);
PRect(Msg.LParam)^.Bottom := PageControl1.ClientHeight;
end;
end;
end;
end;
You can fill in the other three cases if you need them. Tcm_AdjustRect is a message identifier declared in the CommCtrl unit. If you don't have that message in that unit, declare it yourself; its value is 4904.
I suspect this doesn't stop the control from drawing its borders. Rather, it causes the contained TTabSheet to grow a little bigger and cover up the borders.
I'm using Delphi XE8 and the following seems to do the trick:
ATabControl.Tabs.Clear;
ATabControl.Style := TTabStyle.tsFlatButtons;
ATabControl.Brush.Color := clWhite;
You could always use a commercial solution. I would strongly recommend Raize components, which support flat TPageControls with tabs. The component set is very easy to work with, and supports numerous visual enhancements which in my opinion give a better feel to any application.
(source: raize.com)
Drop two TPageControls, one with tabs as Tabs, with a global height equal to the tabs, and one with flatbuttons and Tabvisible properties set to false, which would be aligned under the first one. Then make sure the tab change on the first TPagecontrol makes the tabs also change in the second one.