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Published 20 hours ago • verified publisher icon dfranx

Preview issue

Open azhar-mahadi opened this issue 4 years ago • 1 comments

I am Ubuntu user setting project preview window clear colour alpha set to zero for each project I must change to 1 Application does not exit properly

azhar-mahadi avatar Jul 13 '21 07:07 azhar-mahadi

Thank you very much @azhar-mahadi for reporting this issue--the mention of "alpha" helped me workaround/solve the same/similar issue I encountered: no image being rendered for the preview.

System configuration

I'm running SHADERed on a laptop with elementary OS 5.1.7 (Ubuntu 18.04 based) and Pantheon with integrated graphics:

OpenGL Renderer		: Mesa DRI Intel(R) HD Graphics 4400 (HSW GT2)
X11 Vendor		: The X.Org Foundation
Version		: 1.20.8

Vendor		: Intel Open Source Technology Center
Version		: 3.0 Mesa 20.0.8
More X11 details 
-Extensions-
Composite
DAMAGE
DOUBLE-BUFFER
DPMS
DRI2
DRI3
GLX
Generic Event Extension
MIT-SCREEN-SAVER
MIT-SHM
Present
RANDR
RECORD
RENDER
SECURITY
SHAPE
SYNC
X-Resource
XC-MISC
XFIXES
XFree86-DGA
XFree86-VidModeExtension
XINERAMA
XInputExtension
XKEYBOARD
XTEST
XVideo

(I'm actually using some libraries from Ubuntu Focal in order to get the pre-built binaries to run which could in theory have an impact.)

Symptoms

  • When the application is first launched the "Preview" area only shows a black rectangle--which is very confusing when nothing seems to change the content! :) e.g.:

    Screenshot from 2021-12-22 13 36 26

    Loading any example project does not change the preview.

    At one point I discovered that if you pause the shader & choose a window region to analyze then suddenly the selected area displays the result of the shader in that region!

  • After I found this issue (#235) describing alpha-related problems, I noted that (after some experimentation) by default the "Project" options section had the checkbox "Window alpha channel" unchecked:

    Screenshot from 2021-12-22 13 36 44

  • When I enabled "Window alpha channel" the preview area immediately changed from black to the grey fill color:

    Screenshot from 2021-12-22 13 36 54

  • Then when I closed the dialog via "OK" the preview rendered correctly!

    Screenshot from 2021-12-22 13 37 02

When I opened any other example project the black rectangle problem reappeared and I needed to re-enable "Window alpha channel" again. (Because it seems this setting is stored per-project not application-wide.)

(Initially I tried changing the colour alpha value to 1 which was how I interpreted the original post on this issue but that didn't seem to fix anything for me--so I'm not sure if I misinterpreted the text or if the OP actually has a problem different to mine.)

When I saved a shader project with "Window alpha channel" enabled it would subsequently open & preview correctly.

Further information

  • I also tried running the Win64 version of SHADERed via WINE & it exhibited the same symptoms.

  • A search of the repo seems to show this window alpha functionality was added in this commit: https://github.com/dfranx/SHADERed/commit/38b418eab0e7591efc77222676274f9b214748f0

    But somewhat confusingly the commit message says "Add option to disable window's alpha channel" but seems to default the UseAlphaChannel value to false.

  • The current related code appears to primarily be in these locations:

    • https://github.com/dfranx/SHADERed/blob/729b5fae747668057162a1ed8fab506a9e3a3d20/src/SHADERed/Objects/RenderEngine.cpp#L125-L137
    • https://github.com/dfranx/SHADERed/blob/79e1e03412b423f26354bb064187090f031c4670/src/SHADERed/Objects/ProjectParser.cpp#L189
    • https://github.com/dfranx/SHADERed/blob/79e1e03412b423f26354bb064187090f031c4670/src/SHADERed/Objects/ProjectParser.cpp#L871-L876
    • https://github.com/dfranx/SHADERed/blob/79e1e03412b423f26354bb064187090f031c4670/src/SHADERed/Objects/ProjectParser.cpp#L3367-L3371
    • https://github.com/dfranx/SHADERed/blob/d118369cbc5f18db3596e318c92557760ef0b466/src/SHADERed/UI/PreviewUI.cpp#L1410-L1415
    • https://github.com/dfranx/SHADERed/blob/d118369cbc5f18db3596e318c92557760ef0b466/src/SHADERed/UI/PreviewUI.cpp#L1625-L1628
    • https://github.com/dfranx/SHADERed/blob/70453b03826fb163baa3eb063d067c89e6b1629f/src/SHADERed/UI/OptionsUI.cpp#L1000-L1020

  • Although I note these locations may also be related, given the symptoms I observed:

    • https://github.com/dfranx/SHADERed/blob/d118369cbc5f18db3596e318c92557760ef0b466/src/SHADERed/UI/PreviewUI.cpp#L1630-L1638
    • https://github.com/dfranx/SHADERed/blob/d118369cbc5f18db3596e318c92557760ef0b466/src/SHADERed/UI/PreviewUI.cpp#L1673-L1683

  • Also this commit modified related code (changing the type?):

    • https://github.com/dfranx/SHADERed/blame/729b5fae747668057162a1ed8fab506a9e3a3d20/src/SHADERed/Objects/RenderEngine.cpp#L125

    • https://github.com/dfranx/SHADERed/commit/4733cd1272e7473c51064b1c7a0e75afdd9235a7#diff-32c7025e981cf2b50e5d8bef504664c76c5f4c8b2b1080d5a2c19e952da71617

Next steps

While having found a workaround is useful & means I can continue playing around with SHADERed (although I think I'll probably do more in the browser for now since that seems easier to get rust-gpu working with), a blank screen/lack of preview is obviously not ideal first run experience. :)

(Side note: If I pause the shader, then analyze & then use the debug view, heat map view etc, they are rendered as expected.)

So, I was thinking there would be a couple of things that would be good if we and/or @dfranx could clarify:

  1. What was the original purpose of making the alpha channel optional? What negative impact (if any) does having the alpha channel enabled by default have on other GPU/compositor/WM systems?
  2. Is this actually a bug in some SHADERed code, perhaps in the window/region/texture setup? (It wasn't clear from a brief skim of the different areas, if the alpha channel-related code was interacting as intended, especially given the non-preview views seem to render okay.)
  3. Otherwise, can we determine where in the graphics stack this unintended interaction is happen and, if so, can we detect it so we can handle it automatically?
  4. Can we default to setting it true?
  5. Can we add an application-wide override flag (or change to make the alpha channel setting application-wide rather than per-project) so we don't have to change each project individually?

Such a helpful bunch of questions to dump here. :D

Hopefully this additional context is useful for developing a fix for this issue & if nothing else might provide further details on the workaround if other people run into it.

Thanks for taking the time to read!

Edit 1: Added "Further information" section. Edit 2: Added "Next steps" section.

follower avatar Dec 22 '21 07:12 follower