Kivy not rendering

[Dan Kolle]

Hello everybody,

I have Kivy set up but it is not rendering anything. I use some customized code but the frame buffer is rendered correctly. I checked this with some hard-coded rectangles.

When I debug my application with gDEBugger GL, I can also see that between binding my frame buffer and unbinding it again, nothing happens except for some matrices being set.

I load a KV file and also implement my own build function to add widgets.

To inject my own frame buffer, I use the following class:

http://pastebin.com/hE7mR6im

This translates into the following OpenGL code:

• The first three lines belong to bind().
  
• Then comes RenderContext.draw().
  
• The last three lines belong to unbind() show my debug rectangle which is visible.
  

So far I had no success, even forcing GI_NEEDS_UPDATE to be set does not change anything. Same for dispatching on_draw and on_flip manually.

It would be great if someone could point me in the right direction why RenderContext.draw does not seem to generate any output.

Thanks

Dan

[Dan Kolle]

This is the log output Kivy gives me:

[0:37:53]  [Debug]    Builder: call_fn <kivy.graphics.vertex_instructions.Rectangle object at 0x000000EC1F657948>, key=size, value=<code object <module> at 0x000000EC1F052700, file "data\style.kv", line 27>, 'self.texture_size'

[0:37:53]  [Debug]    Builder: call_fn => value=[52, 15]

[0:37:53]  [Debug]    Builder: call_fn <kivy.graphics.vertex_instructions.Rectangle object at 0x000000EC1F657948>, key=texture, value=<code object <module> at 0x000000EC1F052B80, file "data\style.kv", line 26>, 'self.texture'

[0:37:53]  [Debug]    Builder: call_fn => value=<Texture hash=1014134061616 id=0 size=(52, 15) colorfmt='rgba' bufferfmt='ubyte' source=None observers=1>

[0:37:53]  [Debug]    Builder: call_fn <kivy.graphics.vertex_instructions.BorderImage object at 0x000000EC1F625640>, key=texture, value=<code object <module> at 0x000000EC1F1D6D00, file "app_logo.kv", line 10>, 'self.texture'

[0:37:53]  [Debug]    Builder: call_fn => value=<Texture hash=1014134061336 id=2 size=(250, 250) colorfmt='rgb' bufferfmt='ubyte' source='False|kivy.jpg|0|0' observers=0>

[0:37:53]  [Debug]    Builder: call_fn <kivy.graphics.vertex_instructions.Rectangle object at 0x000000EC1F6577A8>, key=texture, value=<code object <module> at 0x000000EC1F063400, file "data\style.kv", line 111>, 'self.texture'

[0:37:53]  [Debug]    Builder: call_fn => value=<Texture hash=1014134061336 id=2 size=(250, 250) colorfmt='rgb' bufferfmt='ubyte' source='False|kivy.jpg|0|0' observers=0>

[0:37:53]  [Debug]    Builder: call_fn <kivy.graphics.vertex_instructions.BorderImage object at 0x000000EC1F625640>, key=size, value=<code object <module> at 0x000000EC1F1E2C40, file "app_logo.kv", line 11>, 'self.texture_size'

[0:37:53]  [Debug]    Builder: call_fn => value=[250, 250]

[0:37:53]  [Debug]    Builder: call_fn <kivy.graphics.vertex_instructions.Rectangle object at 0x000000EC1F6577A8>, key=pos, value=<code object <module> at 0x000000EC1F063F40, file "data\style.kv", line 113>, 'self.center_x - self.norm_image_size[0] / 2., self.center_y - self.norm_image_size[1] / 2.'

[0:37:54]  [Debug]    Builder: call_fn => value=(0.0, 0.0)

[0:37:54]  [Debug]    Builder: call_fn <kivy.graphics.vertex_instructions.Rectangle object at 0x000000EC1F6577A8>, key=size, value=<code object <module> at 0x000000EC1F0634C0, file "data\style.kv", line 112>, 'self.norm_image_size'

[0:37:54]  [Debug]    Builder: call_fn => value=(100, 100.0)

[0:37:54]  [Debug]    Builder: call_fn <kivy.graphics.vertex_instructions.BorderImage object at 0x000000EC1F625C28>, key=pos, value=<code object <module> at 0x000000EC1F0524C0, file "data\style.kv", line 20>, 'self.pos'

[0:37:54]  [Debug]    Builder: call_fn => value=[100, 100]

[0:37:54]  [Debug]    Builder: call_fn <kivy.graphics.vertex_instructions.Rectangle object at 0x000000EC1F657948>, key=pos, value=<code object <module> at 0x000000EC1F052100, file "data\style.kv", line 28>, 'int(self.center_x - self.texture_size[0] / 2.), int(self.center_y - self.texture_size[1] / 2.)'

[0:37:54]  [Debug]    Builder: call_fn => value=(124, 142)

[0:37:54]  [Debug]    Builder: call_fn <kivy.graphics.vertex_instructions.BorderImage object at 0x000000EC1F625C28>, key=source, value=<code object <module> at 0x000000EC1F052C40, file "data\style.kv", line 22>, 'self.disabled_image if self.disabled else self.state_image'

[0:37:54]  [Debug]    Builder: call_fn => value='atlas://data/images/defaulttheme/button'

[0:37:54]  [Debug]    Atlas: Load <data\images\defaulttheme.atlas>

[0:37:54]  [Debug]    Atlas: Need to load 1 images

[0:37:54]  [Debug]    Atlas: Load <\data\images\defaulttheme-0.png>

[0:37:54]  [Debug]    MyImage: Load <data\images\defaulttheme-0.png>

[0:37:54]  [Debug]    Image: 'data\\images\\defaulttheme-0.png', populate to textures (1)

[Alexander Taylor]

I don't follow - do you mean that kivy itself is broken and doesn't render anything (e.g. all the examples don't work), or specifically that your RenderContext subclass doesn't work?

[Dan Kolle]

I am using a different "provider" than sdl2 so I need my own RenderContext. The rendering by itself seems to work but RenderContext.draw() does not generate any opengl instructions except for some matrices.

Right now I do not know why no OpenGL instructions are generated, the root object is set and compiled_children is generated as well. I use  the kv/app_logo example as a starting point.

Sadly cython is a bit tedious when debugging so I was hoping that someone could point out the place where it would set the projection matrices but then fail to continue to draw any children so I can continue debugging there.

The call to the draw aka apply methods looks fine to me:

> Creator.exe!__pyx_f_4kivy_8graphics_12instructions_16InstructionGroup_apply(__pyx_obj_4kivy_8graphics_12instructions_InstructionGroup * __pyx_v_self) Line 3763 C

  Creator.exe!__pyx_f_4kivy_8graphics_12instructions_6Canvas_apply(__pyx_obj_4kivy_8graphics_12instructions_Canvas * __pyx_v_self) Line 8870 C

  Creator.exe!__pyx_f_4kivy_8graphics_12instructions_13RenderContext_apply(__pyx_obj_4kivy_8graphics_12instructions_RenderContext * __pyx_v_self) Line 11641 C

  Creator.exe!__pyx_f_4kivy_8graphics_12instructions_6Canvas_draw(__pyx_obj_4kivy_8graphics_12instructions_Canvas * __pyx_v_self, int __pyx_skip_dispatch) Line 8709 C

  Creator.exe!__pyx_pf_4kivy_8graphics_12instructions_6Canvas_4draw(__pyx_obj_4kivy_8graphics_12instructions_Canvas * __pyx_v_self) Line 8747 C

  Creator.exe!__pyx_pw_4kivy_8graphics_12instructions_6Canvas_5draw(_object * __pyx_v_self, _object * unused) Line 8731 C

[Dan Kolle]

I noticed that the GI_NO_APPLY_ONCE is set.

I found this comment:

        # Also, flag ourself as GL_NO_APPLY_ONCE, to prevent to reapply all the

        # instructions when the compiler is leaving.

Can it be that no drawing happens at all and the matrix instructions I see are from the compiler?

[Alexander Taylor]

I don't understand - the RenderContext doesn't care if you are using sdl2 or not, it's an opengl abstraction that should work the same regardless of backend.

I don't know what's wrong though, anyway. Maybe you could post a working example demonstrating waht you're trying and the problem you have.

[Dan Kolle]

Good point. I took my render context out of the equation and render directly to OpenGL. So I end up with this now so nothing really changed which is good as expected.

About what I am trying to do. I have Python embedded in one of my applications and I want to use Kivy for the user interface.

I have Image, Window, Label and Text modified so it will work with the native framework of my application.

As far as I have debugged from C++ and Python side everything looks fine now but the draw call to Kivy does not render anything at all. As mentioned I use the app_logo example so I would expect at least some texture bindings to happen.

My tick function which I use to debug the drawing looks like this:

self._kivy._app_window.dispatch('on_draw')
self._kivy._app_window.dispatch('on_flip')

EventLoop.idle()

Currently I am not sure why nothing is drawn as everything should be set up as needed. Also the Kivy log does not show any errors. Only warning I get is related to wm_pen and wm_touch.

Here is the complete log I get from Kivy:
https://www.dropbox.com/s/0ioma8s2lhmhrim/kivy_log.txt?dl=0

[Dan Kolle]

Okay I found the problem. Because I do ticking on my own due to the nature of my application, I extended App.run so it passes a parameter "slave" to runTouchApp. I did not notice that this will still cause stop() to be called. Now the content is displayed as expected.

[Dan Kolle]

Thanks for your help. Your input pushed me in the right direction. :)