Who is taking care about "canvas transparency"?

OK, this is beginning to become an issue that really makes me feel uncomfortable with Xojo. Use the forum search and type “canvas transparency”. WHAT?

So many people having problems with that issue and it is still not usable “cross platform”?

Here my understanding of the use of transparency: I insert a canvas and put a “backdrop” in there in the IDE. The picture used has a working transparent background. The IDE shows a correct image.


You run it on a Mac. It looks OK. Run it on Windows: Crap - not transparent. Even worse: Now I take the image (PNG file) and assign it to the backdrop of the canvas. No transparency any more in no environment. Xojo 2020 2.1. In older versions it looks different - so at least something changed. But it is not working.


If you look around here in the forum I had this other transparency issue .

It came out that I opened a feedback issue - “reproduced”. Not a bug. So Xojo if you are really interested in new users I would suggest to fix things like this with priority. I personnally wasted a lot of time now with this issue and I am going to produce an application with a nice and usable interface. Cross platform.

If anyone could help me to use a (simple) workaround it would be very appreciated. Even more I would appreciate a new Xojo version with these issues fixed. Not only for me but for any developer who expects a behaviour of the system as it can be defined.

Thanks a lot.

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This may help:

In other words, there is no real transparency in Windows with Xojo.

Can you post a little demo project and a link to the assets?

don’t use backdrop property, try drawing it in the paint event instead.


What is the reason not to use the backdrop?

Two things.

  1. To see if that is the problem or not.
  2. Drawing it yourself allows for more control. I realize the OP is on Windows, but there may be a way he can get this work when drawing it himself. Maybe the OP needs to draw the window color into the canvas first. I don’t know.
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That is correct.

Is there any unreal transparency? Did I miss something? :crazy_face:

Yes, Xojo uses a trick to make it look transparant. It copies the background and draws it in the control.

As long Xojo relies on Win32 APIs and Direct2D, it cannot do real transparency, I guess.

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Uuuuhhh - good to know. This may help me with my other problem (in the other thread) - I should not take a transparent canvas but a canvas with the background of the control it is located in instead. Nasty. Anyhow my Mac App looks really pretty now.

Finally I still believe this may be a bit too heavy for newbies.

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Why are you wasting time with that? Xojo already said years ago that “this is windows fault” and that they are not going to do anithing because it is “not” a but but a OS feature…

A workaround, use a custom paited background for the parent and copy that background to the controls before drawing the content.

It is not an OS feature. Proof being that Visual Studio canvas is perfectly transparent.

It is a convenient excuse to blame the OS when in reality, it is a decision from Xojo to cripple purposefully the Windows platform, without the least care for what it does to Xojo users projects.

Where is a the fallacious claim to develop once, complete many ? No offense, but multiplatform, my foot. Any project created on Mac with true transparency will require substantial modifications to compile anything usable for Windows.

That is the reason why I still use 2016R3 for Windows.


That is why I told, dont waste time, they already made the desition.

ha ha! I’m sure there is, in the Unreal engine.

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Jep, sure! :crazy_face: