In Delphi, I've added a Scrollbar component (oriented vertical) to the right side of my form.
I've added a Scrollbar OnChange event so I can change the view of the form and the position of the scrollbar thumb when the user clicks on the UpArrow or DownArrow button with his mouse, and this works fine.
But the OnChange event only seems to get triggered when the mouse button is initially pressed on the arrow.
I notice all scrollbar controls repeat the command and continue scrolling while the mouse remains pressed on the arrow, and I'd like to implement this behavior.
So how can I easily detect if the user has not moved the mouse and continues to press the mouse button while the mouse remains over the arrow?
Conclusion. Somehow something in the scrollbar in my project got corrupted. After I deleted the ScrollBar, and added it again, the problem vanished.
This is one of those tricky ones that took me a lot of time to solve. Thanks for your help. I'm closing this question.
Use the OnScroll event.
The following code adds 'xxx' to a memo as long as the mouse is held down on the scrollbar arrow button. Tested with Delphi 6.
procedure TForm1.ScrollBar1Scroll(Sender: TObject; ScrollCode: TScrollCode;
var ScrollPos: Integer);
begin
Memo1.Lines.Add( 'xxx' );
end;
The usual way to handle auto-repeating is to enable a TTimer and check in the OnTimer() event handler whether the action needs to be performed again, and to deactivate the timer if not. If you need sample code, I seem to remember that the SynEdit control used a similar technique for autoscrolling in drag and drop operations.
If a component does not encapsulate the behaviour you are looking for and you can't easily simulate the behaviour with the methods available you should really subclass the closest component that does most of what you need and add the behaviours that are missing.
I know that some extra work is involved but it really is the better way to go. Now with Delphi, I seem to recall that subclassed components needed a bit of extra work as well to be able to be used from the IDE for form design, maybe this has changed since version 7.
Related
Why OnHScrollChange is not fired in stringgrid in Firemonkey? How should i catch the scrolling event in Stringgrid?
OnHScrollChange is fired when you scroll with the scrollbar thumbgrip or its buttons. It is however not fired by changing the selection with the left and right arrow keys, even if that would result in the thumbgrip of the scrollbar being moved.
If your question is about the latter situation, I kind of agree with you that it should trigger the OnHScrollChange, but then again, I have no idea of any design decisions. You may want to enter a report at Embarcadero's Quality Portal and see how they respond.
Another possibility is to use the OnViewportPositionChange event instead which fires however the viewport position changes. The caveat is that it fires also on vertical scrolling. If this is ok for you then that is your solution.
My goal is to create a simple forms editor like the one that we find on Delphi IDE.
Right now the user can select and add the components making it parent of a TPanel that is the holder of the form. For simplicity, please consider also TPanel as the visual components added to the form.
I have 2 missing parts I want to find out ideas/code to help complete:
1 - how to move the created visual component? The same effect that in IDE for moving the visual component, for example Tpanel, around, chaning its top and left position
2 - how to draw that hooks for the component with focus on the form editor
3 - how to resize using the hooks
I only want the part related to handle the visual part. I am not generating DFM or anything like that.
Simply put your moving code needs to do this:
When the mouse goes down, check if the mouse position is over a control that can be dragged. If so, then set a variable named FDragControl to refer to that control. This code lives in an OnMouseDown event handler.
When the mouse moves, if FDragControl is not nil, move the control. This code lives in an OnMouseMove event handler.
When the mouse goes up, set FDragControl to nil.
That's pretty much all there is to it. The main nuance is that you must also remember the X, Y values of the mouse when the drag commenced. So in your OnMouseDown handler you write:
FStartMousePos := Point(X, Y);
FStartDragControlPos := Point(FDragControl.Left, FDragControl.Top);
And then in the OnMouseMove your position code reads:
FDragControl.Left := FStartDragControlPos.X + (X-FStartX);
FDragControl.Top := FStartDragControlPos.Y + (Y-FStartY);
You will also need to capture the mouse when you start dragging.
The resizing code is similar. Again, you need to decide in the OnMouseDown that you are resizing rather than dragging, but the code still involves handling mouse down, move and up events.
As for painting, you need to force a repaint whenever one of your event handlers changes a property that will influence the visual appearance of your form. You can use the value of FDragControl to decide whether or not to use special drawing of your control and indicate that it is being dragged. And likewise for resizing.
I've not coded up a full working implementation since your question is high level and conceptual. The implementation is down to you.
// I have made this an answer as I have just read your latest update which really should have been made as an edit to your original question but, anyway.
You can download the Cindy Components Pack and use the cyResizer Component which will do pretty much everything you need and is very customisable as well.
You can download it from here: http://sourceforge.net/projects/tcycomponents/
Searching more for an answer I could find these articles:
How to Move and Resize Controls at Run Time
http://delphi.about.com/library/weekly/aa102505a.htm
How to Add Size Handles to Controls being Resized at Run-Time
http://delphi.about.com/library/weekly/aa110105a.htm
Pretty much with all the information to complete this task with source code example.
These articles show how to implement and use a TMover class. I have done it and work correctly.
I have also downloaded the TcyComponents Pack and used the TcyResizer. It is a full featured form editor with pretty much everything that is required for a Delphi like forms editor. I recommend. It comes with source code and works fine with XE2 version.
I have two 100% overlapping panels with different contents on a form.
The first (static display of information) should be visible by default, but the other (user interaction) should replace it if the user moves the mouse near the two - and if the mouse moves away, it should switch back.
Something like this:
if (*the mouse is near*) then
begin
Panel1.Hide;
Panel2.Show;
end
else
begin
Panel2.Hide;
Panel1.Show;
end;
My problem is: where to capture mouse movement?
Each component has its own OnMouseMove handler - of course I could forward each of them to the forms handler, but I'd rather have something a bit more elegant (and easier to maintain).
The perfect solution would be something like Form1.MousePreview := true;.
Another solution would be assigning a generic handler that translates coordinates and calls the forms handler; The assigning could be done in FormCreate.
But that's not as easy as it seems, because one TImage already has its own mouse event handlers.
I have tried OnMouseEnter and OnMouseLeave of the two panels but it didn't work; #1 disappeared, but #2 did not appear. I guess that's because if the mouse leaves Panel2, it should disappear - but it also leaves it if it enters a button on it.
That's why I'd like to use a coordinate based approach to make the check more reliable.
Maybe the two panel method is completely wrong?
Update: Yes, it is, as Remy said.
I am now using a TJVPageList because a TPageControl has visual tabs.
The OnMouseEnter handler of the PageList sets one page, the OnMouseLeave sets the other; But once the mouse moves over the PageList, both pages start flickering.
I have tried adding the event handlers to each page, too, but that made no difference.
Should I check all OnMouseEnter / Leave events to filter out the PageList, the two pages and all components sitting on the pages?
Another update: I am using a TPageControl now, but the behaviour is similar.
It doesn't flicker, but if I move the mouse ontop the TPageControl, no TTabSheet is displayed at all.
Only if I press down the left mousebutton, the UI sheet is displayed. The other sheet is displayed normally if I move away the mouse. (The TJVPageList displays the UI page if I press the left mousebutton, too.)
I have used the mouse event handlers (enter/leave) of the TPageControl and both TTabSheets.
Update 3:
Done it.
The static Panel / TabSheet / JvStandardPage (#1) must not trigger the OnMouseLeave handler.
What you describe might be better served using a single TPageControl instead of two TPanel controls. Use the TPageControl's own OnMouseEnter/Leave events (or intercept the CM_MOUSEENTER/LEAVE messages) to switch the TPageControl.ActivePage as needed.
I'm building a custom control which is to have multiple focus points. For example, within 1 control, let's say there's 3 regions (could be defined as a rect on the canvas) which are to be able to have focus. Depending on which one has focus, I don't want the default Windows dotted line around it, but some special handling. I know nothing about how to even give 1 custom control its own focus.
The original project was a single TPanel with a few VCL controls on it, each of course being its own window, thus having its own focus. But now I'm putting it into a custom class of its own, which these 3 controls will no longer exist (they were only there in version 1 as a prototype) and I need to now somehow mimic the focus in these different regions.
I guess similar to something as simple as a TListBox, where certain items within that control get the focus instead of the entire control its self.
Here's a picture to help demonstrate what I'm making...
The one on the top is the original with the buttons. But the one on the bottom is the new one I'm building which is all custom drawn.
To elaborate, I'd like to see if Windows already has special handling for this type of scenario before I go and re-invent the wheel.
I'm not looking for the "Easiest" way to accomplish this. And I also do not want recommendations to revert back to how I had it before, because there's many reasons I don't want 1 control with multiple other controls within. I just need a yes or no, with an explanation.
More
I just realized the main concern is the use of the tab key. The control has to first get the focus, start the focus on whichever sub-item it's supposed to, then respond to tab on my command until it reaches the end, then pass the tabbing over to the next control. Then it also needs shift+tab as well. How on earth would I implement this tabbing? That's where I got stuck, but it just struck me that this is the main reason I'm asking.
About the handling of the TAB key - it should be something like this: you handle the WM_GETDLGCODE message to indicate that you want to proccess the TAB key, ie
TMyControl = ...
protected
procedure WMGetDlgCode(var Msg: TMessage); message WM_GETDLGCODE;
procedure KeyDown(var Key: Word; Shift: TShiftState); override;
...
procedure TMyControl.WMGetDlgCode(var Msg: TMessage);
begin
inherited;
Msg.Result:= Msg.Result or DLGC_WANTTAB;
end;
and the in the overriden KeyDown method you decide what to do in response of it, something like
procedure TMyControl.KeyDown(var Key: Word; Shift: TShiftState);
begin
if(Key = VK_TAB)then begin
if(ssShift in Shift)then begin
if(first subcontrol is focused) set focus to previous control on parent
else set focus to previous child area
end else begin
if(last subcontrol is focused) set focus to next control on parent
else set focus to next child area
end;
end else inherited;
end;
No you can't get windows to recognize multiple points of keyboard focus inside the same window handle, since each control with a window handle either has, or does not have, keyboard focus. The "inner focus" between multiple controls is up to you to sort out.
As you already knew, the most simple way to accomplish this is to have multiple sub-controls with their own window-handles, which is what you said you are doing:
TMyThreeEditControls = class(TControl) // parent has no window handle!!!!
protected
FEdit1:TEdit;
FEdit2:TEdit;
FEdit3:TEdit;
...
end
In the situation above, the parent control is a TControl, it creates several sub controls, in my example above, all three have their own window handles, and thus Windows can display keyboard focus when you hit tab, and handle mouse focus as part of Windows's common controls library's functionality.
In short, the "composite" approach where you include sub-objects (other controls) in your main control, which you are trying to move away from is in fact, the only way to let Windows do most of the work.
On the other hand, what you might be looking for is not a way to have a control paint itself, but some code to make something look like it is focused, in your own custom painting routines, if that is what you are looking for, you should look into the VCL source code or this link on about.com for examples on how to tell Windows to draw a focus rectangle, etc. The about.com link is an imitation and does not use real windows code to draw focus in a Windows-theme aware way.
Update: it is possible that what you are also looking for is the way to determine if mouse co-ordinates are within a specified rectangle (the rectangle represents a button in your case) and if so, to draw a "hot state" for the button. There are more sub-tasks than this to accomplish if you wish to build a control yourself, I recommend you study existing controls such as TStringGrid and TCategoryButtons in the VCL source code, to see the MouseMove, MouseDown, and MouseUp handling code you will need to do the things you are trying to do. In particular, StringGrid source code is the way to see how the "tab key" can be used within a single control with a single window handle, because in that control the tab key can be used (if the right options are turned on) to navigate among all the cells inside the string grid, as if each one was a separate control, even though it is all one control.
Another way to achieve this is to use one edit box that you re-use for each region that you want to have "focused". This is essentially how Delphi's grids work.
When the user clicks in that area (or hits the tab key into your control) you set the edit controls text to the data in that area, set the edit controls bounds to the area and make it visible. When the user exits the control (by clicking out of it or tabbing) you hide the edit control. If you make your control accept the tab key, you can make it "edit" the next area when they hit tab and exit it when they are in the last area.
Then it's just house keeping to make sure you store the entered data in the right spot in your component.
I have a heavily modified control based on TStringGrid. I want to allow the user to make selections in this grid but restrict the selection one single row (the current row).
Implementation:
When the user presses the left mouse button I am using a dirty hack: On OnMouseDown event I capture the mouse cursor and keep it on the current row. The user can move the mouse device up and down on its pad but the cursor will not go up or down. It will stay on the current row. When the user releases the button (OnMouseUp event), I release the capture.
However, this hack is as I said very dirty. There are several problems. For example, if the user presses the left mouse button (LMB) and then without releasing that button it presses the right button, the associated pop-up menu will pop but the mouse capture will never be released. So, the mouse will be locked in a screen region until the user will has the brilliant idea to click the LMB one more time to unlock the mouse. This may be a bug in D7. There is a separate post about it here: TStringGrid - OnMouseUp is not called!
There is a elegant way to do this?
Edit:
OnSelectCell is not working. OnSelectCell event is called only once when you click the cell. If you keep the button pressed and move the mouse to expand the selection, OnSelectCell will not be called again.
Indeed MoveCurrent appears only in TCustomGrid.MouseDown.
Use the OnSelectCell event and set the CanSelect var parameter depending on whether the ARow parameter is what you want.
A nice solution
Check the options property on TStringGrid
There is an Option called 'goRangeSelect'
Set this to false using the object inspector
Or programatically this can be done by
StringGrid1.Options - [goRangeSelect];
This answer is not elegant at all, but it works.
My solution is NOT to use the PopupMenu property of the StringGrid. Instead I implemented my own PopUpMenu property. Works almost perfect. There is on small problem, the bottom of the pop-up menu appears next to the cursor and not its top.