I have a TStackPanel which I want to add a number of frames into at runtime. The number may vary each time the form is opened.
There seems to be limited information about TStackPanel around, and the examples I can find are in languages other than Delphi.
I have a loop that creates the frame, gives it a unique name and then adds it to the TStackPanel:
for i := 0 to 10 do
begin
mfSubFrame[i] := TMyFrame.Create(Application);
mfSubFrame.Name := name_array[i];
StackPanel1.InsertComponent(mfSubFrame[i]);
end;
This does not put anything in the stack panel. If I change the SP line to:
StackPanel1.InsertControl(mfSubFrame[i]);
then I do get a frame in the SP. It is the last one of the loop as I can tell by the name, the others may be hidden behind it but I can't tell. They are certainly not stacked horizontally like they should.
I have tried various other things like setting the parent of the frames to be the SP, and had a look at things like:
StackPanel1.Components.InsertComponent(mfSubFrame[i]);
and other sub-methods, but had no luck so far.
I suspect it may require a combination of statements, like add a control item as well as the actual component, but as I am working on the basis of trial and error it could be a long time before I stumble on the right combination.
I have never used the TStackPanel before, but it seems like you can add controls to it exactly the same way you add controls to any other windowed control: just create the control and assign its Parent.
For example,
for var i := 1 to 10 do
begin
var Memo := TMemo.Create(Self);
Memo.Parent := StackPanel1;
end;
will add ten memo controls (all owned by Self) to StackPanel1. There is no need to name the controls; referring to components by string name at runtime is an antipattern. (So is using FindComponent.)
InsertComponent() changes a component's Owner, which has no effect on visual display. You are creating each frame with Application as its Owner, and then changing its Owner to StackPanel1. You should assign the desired Owner when calling the component's constructor.
InsertControl() changes a control's Parent, which does affect visual display. You are creating each frame without a Parent, and then changing its Parent to be StackPanel1. You should be using the actual Parent property, not calling InsertControl() directly.
That being said, TStackPanel has a ControlCollection property that you are not doing anything with. That collection manages the actual stacking.
If needed 1, for each frame, try calling StackPanel1.ControlCollection.Add(), and then assigning the frame to the TStackPanelCollectionItem.Control property.
1: I don't have the source code for TStackPanel to look at, but I suspect TStackPanel probably handles this automatically for UI controls dropped onto it at design-time, but you might need to perform it manually for controls that you create dynamically at runtime. I'm not sure.
Related
I have noticed something very strange. I am persisting the top, left, width, and height properties of a form when it is closing, and using this information to restore the form's last position when it is once again opened by calling SetBounds using the previously stored information. This works well, but only if the form's Position property is set to poDefault at design time. If set to something else, such as poDesigned, poScreenCenter, or poMainFormCenter, SetBounds does not restore the form's previous position and size.
Here's the strange part. What appears to matter is what the Position property is set to at design time. I can change the value of this property at runtime to poDefault and the call to SetBounds still does not work correctly. I have tried something like the following
if Self.Position <> poDefault then
Self.Position := poDefault;
in both the form's OnCreate event handler, as well as from an overridden constructor (and have set Position to poDefault in the constructor, and called SetBounds in the OnCreate event handler). In all cases, changing the form's Position property to poDefault at runtime does not fix the problem that I've observed with SetBounds. The only consistent pattern that I have found is that SetBounds works as it should only if the form's Position property was poDefault at design time.
There are other things that I've noticed with respect to how SetBounds works when a form's Position property is not set to poDefault at design time. For example, a form whose Position property is set to poScreenCenter at design time will not necessarily appear centered on the screen if you call SetBounds. However, it does not appear in the top-left location defined by SetBounds, nor does it respect the width and height specified in the call to SetBounds. Let me repeat, however, that I am setting the Position property of the form to poDefault before calling SetBounds. I've even stuck a call to Application.ProcessMessages between the two operations, but that doesn't fix the problem.
I have tested this extensively with Delphi 10.1 Berlin running on Windows 10. I have also tested it using Delphi XE6 on Windows 7. Same results.
If you have doubts, create a VCL application with four forms. On the first form place three buttons, and add something like the following OnClick to each button:
with TForm2.Create(nil) do
try
ShowModal;
finally
Release;
end;
where the constructor creates TForm2, then TForm3 and TForm4.
On the OnCreate of forms 2 through 4, add the following code:
if Self.Position <> poDefault then
Self.Position := poDefault;
Self.SetBounds(500,500,500,500);
On form2, set Position to poDefault, on form3 set Position to poScreenCenter, and on form4 leave Position set to the default, poDefaultPosOnly. Only form2 will appear at 500, 500, with a width of 500 and a height of 500.
Does anyone have a logical explanation for this result?
poDefault and friends mean "let Microsoft Windows position this form's window when the form would create and show it".
You just created Delphi object - but I wonder if it also has created/shown Windows object (HWND handle and all corresponding Windows internal structures). Especially with themed applications, not ones using standard pre-XP look and feel - they tend to ReCreateHWND when showing, because pre-loading those fancy Windows Themes is relatively expensive operation and only should be done when needed.
I think your default bounds (every property value set in the constructor might be considered a default non-tuned value, to be tuned later after object being constructed) are correctly ignored when you (or TApplication - that makes little difference for the topic) finally do FormXXX.Show.
It is during "make me a window and display it" sequence when your form looks at its properties and tells to MS Windows something like "now I want to create your internal HWND-object and position it at default coordinates/size at your discretion".
And that is absolutely correct behaviour - otherwise WHEN and HOW could TForm apply the Position property??? It just makes no sense to ask Windows for coordinates of a window that does not exists on the screen yet and maybe never would. Windows offers default coords/sizes for the this very second it being asked, looking how many other windows are there and where they are positioned ( and AMD/NVidia video drivers might also apply their correction to it).
It would make little sense, to acquire defaults now, and apply them two hours later when everything would probably be different - different amount of other windows and different positions of those, different set of monitors attached and with different resolutions, etc.
Just consider a "desktop replacement" type of notebook. It was set upon the table connected to large stationary external monitor. Then - let's imagine it - I run your application and it created the tform Delphi object and in the constructor it asked MS Windows for position - and Windows rightfully offered the position at that very secondary large monitor. But then an hour later I unplugged the notebook and walked away with it. Now an hour later I tell your application to show the form - and it will do what? display it with coordinates belonging to that now-detached external display? Outside of the viewport of the notebook's internal display that I only have at the moment? Should this form be displayed in the now "invisible" position just because when I started the application back then that spot was still visible there yet??? Way to confuse users for no gain, I think.
So the only correct behaviour would be to ask Windows for default coords this very second WHEN the form is going from hidden to visible and not a second earlier.
And that means that if you want to move your form - you should do it after it was being show. Place your Self.SetBounds(500,500,500,500); into OnShow event handler. So let the MS Windows materialize your form into default position like required by poDefault in Position property - and move your Window after that. Attempts to move the window that does not exist yet look correctly futile to me.
Either PRESET your form ( in constructing sequence) to explicitly ignore MS Windows defaults and use pre-set cords (via poDesigned value), or let the form ask Windows coordinates, but MOVE it with SetBounds after it got visible via OnShow handler.
I'm looking for the correct way in order to remove a TChart and deallocate all the memory.
I am using Delphi2007 with the standard TeeChart 7
I create the TChart programmatically:
var parentform: TForm;
begin
newchart:= TChart.Create(parentform);
newchart.Parent:= parentform;
...
Then, I want to remove only the chart from the form (not closing the form itself), but I get only that the chart becomes blank and stays on the form:
newChart.FreeAllSeries;
FreeAndNil(newChart);
if I use
NewChart.Parent := nil,
I don't see the chart anymore, but I think the TChart object still exists (until the parentform is destroyed). Is there a specific method for doing this?
Thank you
The most straightforward way to get rid of a TChart control, or just about any control, for that matter, is to call Free on it:
newChart.Free;
You can call FreeAndNil instead if you wish. That has the same effect of calling Free, but also sets the variable's value to nil. That's useful if you later test the variable's value to detect whether you still have access to the control. If you never reference the variable again, then FreeAndNil doesn't get you much.
The control will automatically free the other things it owns, such as the series you manually freed with FreeAllSeries. You don't need to free them yourself.
Merely clearing the control's Parent property does not free the control. You can prove that by re-assigning the Parent property and watching as the control re-appears on the screen. That wouldn't happen if the control had ceased to exist.
If the control remains visible on the screen after you free it, then you have other problems. Maybe the parent control hasn't repainted itself properly. You might try calling Refresh on the parent control. You might also have multiple controls visible. After all, the question's code creates two chart controls, so maybe one of them is still visible, and you've mistaken it for the control you destroyed.
Please help me with my question.
I have TreeView and Frames, how can I shift them if I click on an item of TreeView?
Is it better to use PageControl (PageControl1.Pages[i].TabVisible := false;) instead of Frames or Frames fit better?
Thank you very much!
To answer your first question "how to ... using a TreeView?" : Implement the OnChange event of the TreeView. The node parameter refers to the newly selected item.
About your second question "Should I use Frames or a PageControl?" : Well, one does not exclude the other and you perfectly can use both. Indeed, I advice to do so when you use the contents of such a TabPage multiple times. In those cases, place the Frame with Align = alClient on your TabPage.
Frames are usefull to design an arbitrary reusable container. For instance: you could set the same FrameType on every Page of the PageControl, assuming they all look the same but each working with different data.
Another possible minor advantage of using frames is not to get confused about all the controls on the TabPages.
But if every TabPage is unique in terms of visual style or control layout, then it's perfectly ok to not use frames and design the pages on the PageControl directly.
And about the shifting part: I don't exactly understand what you want to accomplish by setting the visibility of a tab, but shifting to another page (depending entirely on your implementation) based on the node could be as simple as:
procedure TForm1.TreeView1Change(Sender: TObject; Node: TTreeNode);
begin
PageControl1.ActivePageIndex := Node.Index;
end;
If I am using Delphi at design time, then when I copy/paste a group of components at design time, the pasted components are slightly offset from their originals.
However, I am developing a GUI which allows users to develop a GUI for another app. When I cut/paste the pasted components lie directly over the originals. Is there are way to offset them slightly?
Since you have the basic copy/paste working, the next bit is a fairly simple extension to what you already have.
Pasting does of course - presumably - paste the copied controls with their copied property values, so yes they will over-lay on top of the original controls from which they were copied.
To get off-setting behaviour, you will have to do some "nudging" of the pasted controls after they have been pasted. If you cannot get a list of the pasted controls more directly, then one way to derive such a list would be to take a copy of the Components collection of the target form before pasting, then after pasting iterate over the Components collection once again - any item now in the collection and not in the "original" list must have been pasted and you can apply your Left/Top nudges to those as required.
list := TList.Create;
try
for i := 0 to Pred(dest.ComponentCount) do
list.Add(dest.Components[i]);
// Do your pasting
for i := 0 to Pred(dest.ComponentCount) do
if list.IndexOf(dest.Components[i]) = -1 then
// Nudge dest.Components[i]
finally
list.Free;
end;
That should get you at least heading down the right direction I think.
NOTE: The above code assumes you are dealing (potentially) with TComponent derived classes (i.e. non-visual components). If you are dealing only with TControl descendants then you could optimise by working with the ControlCount and Controls of the destination container control (not necessarily the form).
Also, the Left/Top position of a TComponent is stored in the lo/hi word of the public DesignInfo property, so your nudge code will need to take that into account and deal with TComponent derived controls differently from TControl if you are working with non-visual components as well as visual controls.
I have an application that uses a frame extensively and needs to hide/show certain buttons depending on which form is active at the time. In order to keep the buttons neat and organized appropriately, I have put them on panels and show or hide the panels as needed for each form. My problem is when each form is initially created, the panels on the frame are out of order even though I am explicitly telling them which order to put themselves into. After I hide and re-show the form, the panels are in the correct order. Any suggestions on how to keep them in the proper order from the very beginning?
Instead of giving the panels explicit positions, try giving them alignments. They tend to stick better than way, and they do a better job of resizing if you resize the form.
You can also try using a stackpanel (or was it flowpanel?) as parent for the panels. Then you will have a order instead of a position to manipulate.
Maybe you can have a look at the DevExpress LAyoutControl? It helps us creating interfaces that always look good, no matter if we show or hide certain groups / panels. It even allows for run-time customization of the interface, if you want that!
You may try to organize them by coordinates i.e.: setting Top and Left. Unless your panels are aligned, this will always work (but it takes bit lot of work).
I had this problem and I found that the solution was to do this in FormCreate (or in a CMShowingChanged method of your frame):
MyPanel1.Align := alNone;
MyPanel2.Align := alNone;
MyPanel1.Align := alBottom;
MyPanel2.Align := alBottom;
Restore in the order that you need - this seemed to sort out the order visually.