I created a Canvas Object with 3 Picture Buffers. On the Main Window CanvasI Drawing Lines & Text in Extend P2Buffer() Array Frames when the Canvas Width exceeded. When it’s exceeded I add a Scroll Bar Control. All this code work perfectly with the width scroll Bars the width of the picture (Thanks you Paul Lefebvre in your Xojo Canvas Video).The Problem is when the Cropped Picture to Window2 Canvas2 Which is instantiated from same Canvas Object with XBuffer. The Window2 Canvas2.Invalidate Won’t Launch the Paint Event. Sorry for too many words.
//Canvas Object
Dim P1Buffer, P2Buffer(), XBuffer As Picture
Canvas Object Paint Event
If XBuffer <> Nil Then
g.DrawPicture(XBuffer, Canvas2.mXScroll, 0)
End If
Crop Method in Window 2
Dim W1, H1, W2, H2, iCrop As Integer
// Paint Event won't Launch
//Calculate unused end tab area to crop off 224 pixels at the end.
iCrop = Window1.Canvas1.Width - (Window1.Canvas1 - 224)
//Resize
W2 = Window1.Canvas1.P2Buffer.Width
H2 = Window1.Canvas1.Height
//Original Size - Minus End Unused Area iCrop
W1 = Window1.Canvas1.P1Buffer.Width - iCrop
H1 = Window1.Canvas1 P1Buffer.Height
Canvas2.XBuffer = New Picture(W2, H2)
Canvas2.XBuffer.Graphics.DrawPicture(Window1.P2Buffer, _ // Resized Picture load to XBuffer
0, 0, W2, H2, _ // scaled size
0, 0, W1, H1) //Original Size
mXScroll = 0
HSclBarStaff.Visible = True
//Does Not Launch XBuffer in Paint Event in the Canvas Object. Not to Drawing XBuffer to //Window2 Canvas2 !??? Tried Canvas2.Refresh Too.
Canvas2.Invalidate
You’re trying to invalidate Canvas2 from within the paint event of another canvas, it seems. That looks like an odd choice.
When do you expect to invalidate Canvas2 in the app’s workflow?
Hi Arnaud - The above Method is fired from a Button Event in Window 2. The 2nd Window Saves it as a Graphic Picture File. The Cropped Window2.Canvas2.XBuffer content loads and is there I can see it in Debugging. It just won’t show up on the Canvas2.Invalidate. I even put a Break Point in the Canvas Object Paint Event. It’s not Launching the Paint Event. I don’t know if there is a Width Out of Bounds that prevents the Paint Event to Launch if the Horizontal Scroll Bar Control is not loading right to extend the width. It works with another set of Canvases that work the same way from a Main Window Canvas sharing the same Canvas Object but they have the same Height & Width or less Width when Cropped.
My Image is in a Canvas Graphics Buffer. Examples from the Eugene Dakins Canvas pdf Book.
Below is from Xojo Canvas Docs. for Backdrop
You should not assign a new picture to the backdrop of the control when being inside the Paint event of that control.
I’ve even tried Canvas2.Refresh getting the same result. It usually winds up being something real simple I’m overlooking. I seem to always get myself into those kind of coding predicaments.
Thank You though for another possible way to try. I’ll see if I find a way pass Canvas.Backdrop from the Graphic.Buffer.
Your description looks a bit overcomplicated to me, for the goal you’re attempting, and I can’t say I understand your specific setup well.
That being said, what I’d do in your case is to test manually. E.g. you may implement (just for the time of testing) the MouseDown event of your canvas and put “me.invalidate” in there. Then run your app and click the canvas. Then you’ll know whether your original issue is a timing one or rather something else. If it refreshes as expected when you click on the canvas, the problem lies on the moment/location of the failing code; otherwise, there’s something else going on (e.g. called on the wrong canvas or that line of code not being reached at all).
If not already done, try adding system.DebugLog "I'm here!" just before calling the Invalidate method, to be sure the statement is encountered.
Hi Arnaud - Sorry I didn’t get back to you. I had to get a nights sleep with a fresh start on this. We are all in different time zones. These are some great testing ideas I have never even thought of. So to recap - I’m trying the mouse down event on the canvas 1st. then I’ll put a break point on me.Invalidate in the event,
I put a mouse down event in both the canvases on my 2nd window. The working canvas me. Invalidate executes the Paint Event in the Canvas Object. The Canvas that is giving me all the problems does not. It definitely proves that it is not launching the Paint Event for that Canvas Object.
I tried the next test system.DebugLog "I'm here!" just before calling the Invalidate. It didn’t really do anything. It just step through like normal debug. I’ve never used this before. I’m going into the Xojo Docs on how to use it,.
I do have a 3rd party Plug In called Elastic Window for resizing the windows for different graphics settings on computers. I noticed it runs the window resize window methods before launching the Paint Event on the working Canvas. It’s never has given me any problems before & has always worked. It could be that, being it has not been supported for some year.
Just in case. hen running the application if you have a Break or a debug point, go to the ide, click in the bottom right button to see the messages as:
Or, when the application quit, click on the same button and you can see your System.DebugLog (on macOS; I do not recall how it works on Windows, sorry).
I just got a creative idea. I’m going to move the Method from the 2nd Window to the Canvas Object to try and get it to work from there. I got nothing else to lose. I’m past trying the same thing over & over and expecting a different result. I’ll keep you all informed of what happens.
Invalidate (and Refresh) both say update the image at some point in the future. Refresh(True) forces a refresh now (or is supposed to) I don’t suppose that would make a difference, I see nobody else has suggested that.
Put the code in a Button,
Be sure tp have a Canvas1 on the same window
Run
Load a small (< 1000 pixels wide) image and watch.
It works here (macOS, Wojo 2024r4.3, last sequoia).So modify the resize line and load your image.
Var picFile As FolderItem
picFile = FolderItem.ShowOpenFileDialog("")
If picFile <> Nil And picFile.Exists Then
Var pic As Picture
pic = Picture.Open(picFile)
Var newPict As New Picture(400,400)
newPict.Graphics.DrawPicture(Pic,0.0,0.0, 400.0,400.0, 0.0,0.0,pic.Width,pic.Height)
If newPict = Nil Then
// Not enough memory
Return
End If
Canvas1.Backdrop = newPict
Canvas1.Refresh
End If
Thank You Emile - I think you have the closest solution. I’m just going to remove the canvas from the 2nd window and just Save the graphic Picture directly from the original Canvas1 in Window1. instead of trying to pass it to Canvas2 in Window2 has been a disaster with the extended scroll bar Width. It just does not like it. I’m working on changing it now.
