Can't get a rendering context, wglCreateContext fails

[dedndave]

interesting   :t

i see where i may have a problem....
i am just getting to "translating" the NextFrame code
it seems they use the global HDC for SwapBuffers
so, maybe it should be retained for the life of the process
although, GetDC is pretty fast - i guess you could get/release each time

[GoneFishing]

...
i learned that i can use glGetString(GL_VERSION) to get my version level
on my old XP machine, i get 1.4.0, a far cry from the 3+ or whatever is current
...

Seems like  version 4.4
In the DirectX SDK  there's an example listing the device capabilities ...
... thinking of doing it for OpenGL

[dedndave]

Seems like  version 4.4

is that under windows 7 ?

[GoneFishing]

Seems like  version 4.4

is that under windows 7 ?

under Windows 8, Dave

EDIT: Just called glGetString with GL_EXTENSIONS parameter - the message box didn't fit the screen! Then I saved the output to file
GL_EXTENSIONS.TXT

GL_AMD_multi_draw_indirect GL_AMD_seamless_cubemap_per_texture GL_ARB_arrays_of_arrays GL_ARB_base_instance GL_ARB_bindless_texture GL_ARB_blend_func_extended GL_ARB_buffer_storage GL_ARB_clear_buffer_object GL_ARB_clear_texture GL_ARB_color_buffer_float GL_ARB_compatibility GL_ARB_compressed_texture_pixel_storage GL_ARB_conservative_depth GL_ARB_compute_shader GL_ARB_compute_variable_group_size GL_ARB_copy_buffer GL_ARB_copy_image GL_ARB_debug_output GL_ARB_depth_buffer_float GL_ARB_depth_clamp GL_ARB_depth_texture GL_ARB_draw_buffers GL_ARB_draw_buffers_blend GL_ARB_draw_indirect GL_ARB_draw_elements_base_vertex GL_ARB_draw_instanced GL_ARB_enhanced_layouts GL_ARB_ES2_compatibility GL_ARB_ES3_compatibility GL_ARB_explicit_attrib_location GL_ARB_explicit_uniform_location GL_ARB_fragment_coord_conventions GL_ARB_fragment_layer_viewport GL_ARB_fragment_program GL_ARB_fragment_program_shadow GL_ARB_fragment_shader GL_ARB_framebuffer_no_attachments GL_ARB_framebuffer_object GL_ARB_framebuffer_sRGB GL_ARB_geometry_shader4 GL_ARB_get_program_binary GL_ARB_gpu_shader5 GL_ARB_gpu_shader_fp64 GL_ARB_half_float_pixel GL_ARB_half_float_vertex GL_ARB_imaging GL_ARB_indirect_parameters GL_ARB_instanced_arrays GL_ARB_internalformat_query GL_ARB_internalformat_query2 GL_ARB_invalidate_subdata GL_ARB_map_buffer_alignment GL_ARB_map_buffer_range GL_ARB_multi_bind GL_ARB_multi_draw_indirect GL_ARB_multisample GL_ARB_multitexture GL_ARB_occlusion_query GL_ARB_occlusion_query2 GL_ARB_pixel_buffer_object GL_ARB_point_parameters GL_ARB_point_sprite GL_ARB_program_interface_query GL_ARB_provoking_vertex GL_ARB_robust_buffer_access_behavior GL_ARB_robustness GL_ARB_sample_shading GL_ARB_sampler_objects GL_ARB_seamless_cube_map GL_ARB_seamless_cubemap_per_texture GL_ARB_separate_shader_objects GL_ARB_shader_atomic_counters GL_ARB_shader_bit_encoding GL_ARB_shader_draw_parameters GL_ARB_shader_group_vote GL_ARB_shader_image_load_store GL_ARB_shader_image_size GL_ARB_shader_objects GL_ARB_shader_precision GL_ARB_query_buffer_object GL_ARB_shader_storage_buffer_object GL_ARB_shader_subroutine GL_ARB_shader_texture_lod GL_ARB_shading_language_100 GL_ARB_shading_language_420pack GL_ARB_shading_language_include GL_ARB_shading_language_packing GL_ARB_shadow GL_ARB_stencil_texturing GL_ARB_sync GL_ARB_tessellation_shader GL_ARB_texture_border_clamp GL_ARB_texture_buffer_object GL_ARB_texture_buffer_object_rgb32 GL_ARB_texture_buffer_range GL_ARB_texture_compression GL_ARB_texture_compression_bptc GL_ARB_texture_compression_rgtc GL_ARB_texture_cube_map GL_ARB_texture_cube_map_array GL_ARB_texture_env_add GL_ARB_texture_env_combine GL_ARB_texture_env_crossbar GL_ARB_texture_env_dot3 GL_ARB_texture_float GL_ARB_texture_gather GL_ARB_texture_mirror_clamp_to_edge GL_ARB_texture_mirrored_repeat GL_ARB_texture_multisample GL_ARB_texture_non_power_of_two GL_ARB_texture_query_levels GL_ARB_texture_query_lod GL_ARB_texture_rectangle GL_ARB_texture_rg GL_ARB_texture_rgb10_a2ui GL_ARB_texture_stencil8 GL_ARB_texture_storage GL_ARB_texture_storage_multisample GL_ARB_texture_swizzle GL_ARB_texture_view GL_ARB_timer_query GL_ARB_transform_feedback2 GL_ARB_transform_feedback3 GL_ARB_transform_feedback_instanced GL_ARB_transpose_matrix GL_ARB_uniform_buffer_object GL_ARB_vertex_array_bgra GL_ARB_vertex_array_object GL_ARB_vertex_attrib_64bit GL_ARB_vertex_attrib_binding GL_ARB_vertex_buffer_object GL_ARB_vertex_program GL_ARB_vertex_shader GL_ARB_vertex_type_10f_11f_11f_rev GL_ARB_vertex_type_2_10_10_10_rev GL_ARB_viewport_array GL_ARB_window_pos GL_ATI_draw_buffers GL_ATI_texture_float GL_ATI_texture_mirror_once GL_S3_s3tc GL_EXT_texture_env_add GL_EXT_abgr GL_EXT_bgra GL_EXT_bindable_uniform GL_EXT_blend_color GL_EXT_blend_equation_separate GL_EXT_blend_func_separate GL_EXT_blend_minmax GL_EXT_blend_subtract GL_EXT_compiled_vertex_array GL_EXT_Cg_shader GL_EXT_depth_bounds_test GL_EXT_direct_state_access GL_EXT_draw_buffers2 GL_EXT_draw_instanced GL_EXT_draw_range_elements GL_EXT_fog_coord GL_EXT_framebuffer_blit GL_EXT_framebuffer_multisample GL_EXTX_framebuffer_mixed_formats GL_EXT_framebuffer_multisample_blit_scaled GL_EXT_framebuffer_object GL_EXT_framebuffer_sRGB GL_EXT_geometry_shader4 GL_EXT_gpu_program_parameters GL_EXT_gpu_shader4 GL_EXT_multi_draw_arrays GL_EXT_packed_depth_stencil GL_EXT_packed_float GL_EXT_packed_pixels GL_EXT_pixel_buffer_object GL_EXT_point_parameters GL_EXT_provoking_vertex GL_EXT_rescale_normal GL_EXT_secondary_color GL_EXT_separate_shader_objects GL_EXT_separate_specular_color GL_EXT_shader_image_load_store GL_EXT_shadow_funcs GL_EXT_stencil_two_side GL_EXT_stencil_wrap GL_EXT_texture3D GL_EXT_texture_array GL_EXT_texture_buffer_object GL_EXT_texture_compression_dxt1 GL_EXT_texture_compression_latc GL_EXT_texture_compression_rgtc GL_EXT_texture_compression_s3tc GL_EXT_texture_cube_map GL_EXT_texture_edge_clamp GL_EXT_texture_env_combine GL_EXT_texture_env_dot3 GL_EXT_texture_filter_anisotropic GL_EXT_texture_integer GL_EXT_texture_lod GL_EXT_texture_lod_bias GL_EXT_texture_mirror_clamp GL_EXT_texture_object GL_EXT_texture_shared_exponent GL_EXT_texture_sRGB GL_EXT_texture_sRGB_decode GL_EXT_texture_storage GL_EXT_texture_swizzle GL_EXT_timer_query GL_EXT_transform_feedback2 GL_EXT_vertex_array GL_EXT_vertex_array_bgra GL_EXT_vertex_attrib_64bit GL_EXT_import_sync_object GL_IBM_rasterpos_clip GL_IBM_texture_mirrored_repeat GL_KHR_debug GL_KTX_buffer_region GL_NV_bindless_multi_draw_indirect GL_NV_bindless_texture GL_NV_blend_equation_advanced GL_NV_blend_square GL_NV_compute_program5 GL_NV_conditional_render GL_NV_copy_depth_to_color GL_NV_copy_image GL_NV_depth_buffer_float GL_NV_depth_clamp GL_NV_draw_texture GL_NV_ES1_1_compatibility GL_NV_explicit_multisample GL_NV_fence GL_NV_float_buffer GL_NV_fog_distance GL_NV_fragment_program GL_NV_fragment_program_option GL_NV_fragment_program2 GL_NV_framebuffer_multisample_coverage GL_NV_geometry_shader4 GL_NV_gpu_program4 GL_NV_gpu_program4_1 GL_NV_gpu_program5 GL_NV_gpu_program5_mem_extended GL_NV_gpu_program_fp64 GL_NV_gpu_shader5 GL_NV_half_float GL_NV_light_max_exponent GL_NV_multisample_coverage GL_NV_multisample_filter_hint GL_NV_occlusion_query GL_NV_packed_depth_stencil GL_NV_parameter_buffer_object GL_NV_parameter_buffer_object2 GL_NV_path_rendering GL_NV_pixel_data_range GL_NV_point_sprite GL_NV_primitive_restart GL_NV_register_combiners GL_NV_register_combiners2 GL_NV_shader_atomic_counters GL_NV_shader_atomic_float GL_NV_shader_buffer_load GL_NV_shader_storage_buffer_object GL_ARB_sparse_texture GL_NV_texgen_reflection GL_NV_texture_barrier GL_NV_texture_compression_vtc GL_NV_texture_env_combine4 GL_NV_texture_expand_normal GL_NV_texture_multisample GL_NV_texture_rectangle GL_NV_texture_shader GL_NV_texture_shader2 GL_NV_texture_shader3 GL_NV_transform_feedback GL_NV_transform_feedback2 GL_NV_vertex_array_range GL_NV_vertex_array_range2 GL_NV_vertex_attrib_integer_64bit GL_NV_vertex_buffer_unified_memory GL_NV_vertex_program GL_NV_vertex_program1_1 GL_NV_vertex_program2 GL_NV_vertex_program2_option GL_NV_vertex_program3 GL_NVX_conditional_render GL_NVX_gpu_memory_info GL_NVX_nvenc_interop GL_OES_compressed_ETC1_RGB8_texture GL_SGIS_generate_mipmap GL_SGIS_texture_lod GL_SGIX_depth_texture GL_SGIX_shadow GL_SUN_slice_accum GL_WIN_swap_hint WGL_EXT_swap_control

I think each of those extensions has a description ... I'll go and think about that

[dedndave]

mine fits - lol

XP mce2005 sp3, opengl v 1.4.0

[hamper]

Now things are getting VERY WIERD INDEED!
I added some printf statements into the program, to output to a console window the values for the window handle, device context and rendering context at various points in the program (the amended program and the output is attached).
It has to be a console build, but it still displays the (empty) window when it runs.

THERE ARE TWO VERY WIERD THINGS GOING ON:

1. At the start, all the values are 0. But after the window is up, I suddenly, automatically get a device context -- even though nothing in the code in between has altered in any way the value of my global variable dchandle.

2. For some reason, my global variable winhandle suddenly reverts back to 0, even though nothing that I can see has changed its value in my code. I had always thought that global variables still had scope within a procedure anyway.

[GoneFishing]

Finally I found reading I'd have started with first!
Open it , Read it , Enjoy it !
Platform specifics: Windows

EDIT: here's info about OpenGL Extensions

[hamper]

Re. my previous post, I also noticed that the sequence I was expecting...

      "Start...
      "After window up...

isn't the sequence that actually happens.

The actual sequence is...

      "Start...
      "Before initialisation...
      "After initialisation...
      "After window up...

So the window procedure must get called automatically, with a WM_CREATE message, before the message loop even starts.
That explains where my "phantom" device context is coming from, but it still doesn't explain (as far as I can see) why my global variable 'winhandle' suddenly gets reset to zero.
(And I still can't get a rendering context)

[hamper]

IT'S FINALLY ALL DROPPED INTO PLACE!
LIKE A EUREKA MOMENT ARCHIE,

The window procedure gets called automatically with a WM_CREATE message even before CreateWindowExA returns! So the initialisation sequence doesn't even have a window handle yet, because CreateWindowExA hasn't yet returned with one. So I can't even push a window handle yet, and that's why nothing works.

Now that I know what the actual sequence of operations is behind the scenes, it should be a simple matter to finally organise the code into the correct sequence for getting everything up and running.

TTFN

[dedndave]

that's right
the earliest moment that your program knows the window handle is during WM_CREATE
when you call CreateWindowEx, the WM_CREATE message is sent to the WndProc
if WM_CREATE returns a value of -1 in EAX, window creation fails, and CreateWindowEx returns 0
if WM_CREATE returns any other value (should be 0) in EAX, window creation is successful and CreateWindowEx returns a handle
of course, this is only true if all the CreateWindowEx parameters are valid

the point is, the WM_CREATE code executes before CreateWindowEx returns to the caller
i often initialize the global hwndMain variable in the first few lines of WM_CREATE code, rather than after the CreateWindowEx call

Code Select Expand

    .if uMsg==WM_CREATE
        mov     edx,hWnd          ;from the WndProc parameter
        mov     hwndMain,edx

; rest of init code

        xor     eax,eax           ;WndProc returns 0 in EAX

[jj2007]

So the initialisation sequence doesn't even have a window handle yet, because CreateWindowExA hasn't yet returned with one.

Congrats, you are on the right track now :t

There is one obvious problem:

Code Select Expand

   initialiseopengl:
      push winhandle
      call GetDC
You are pushing zero here

[dedndave]

also....
when you call GetDC with hWnd=0, you get the desktop DC
HWND_DESKTOP is a windows constant, and has a value of 0
so - you still get an HDC - just not the one you are looking for

after making a few changes, i got your code to run
and, the triangle spins like a bat out of hell - lol
you may want to move the update call out of the message loop, now

[hamper]

Well dedndave, perhaps you could post your program so that I can see how it should be done, because I've tried just about every permutation I can possibly think of, and all I EVER get is (sometimes) a very brief flash of black, then the same little window again, and again, and again, .......... No matter what I try, it just doesn't work.

Maybe you could also zip up the .exe version as well. At least I'll be able to see FOR THE FIRST TIME what it's supposed to look like when it runs.

[GoneFishing]

BTW could you tell us which IDE you use ,
also which version of ML ?

[jj2007]

At least I'll be able to see FOR THE FIRST TIME what it's supposed to look like when it runs.

A working version is available since reply #44 - just run the attached exe.