unable to use custom font

[sadguitarius]

Hi, not sure if this is the best place to post, but I'm struggling trying to adapt the demo to use a custom font. I've attempted to pull the relevant code from imgui-highdpi-sapp.cc in the sokol-samples repo and adapt it to C (and copied over the header with font data). I can build and run the demo, but all text is missing. As in there's not even empty space or white blocks where text should be, just nothing at all. I'm sure I'm misunderstanding something, but this looks to me like it should work. Thank you!

//------------------------------------------------------------------------------
//  Simple C99 cimgui+sokol starter project for Win32, Linux and macOS.
//------------------------------------------------------------------------------
#include "cimgui.h"
#include "imgui_font.h"
#include "sokol_app.h"
#include "sokol_gfx.h"
#include "sokol_glue.h"
#include "sokol_imgui.h"
#include "sokol_log.h"

static struct {
  sg_pass_action pass_action;
} state;

static void init(void) {
  sg_setup(&(sg_desc){
      .environment = sglue_environment(),
      .logger.func = slog_func,
  });
  // simgui_setup(&(simgui_desc_t){ 0 });

  // setup sokol-imgui, but provide our own font
  simgui_desc_t simgui_desc = {};
  simgui_desc.no_default_font = true;
  simgui_desc.logger.func = slog_func;
  simgui_setup(&simgui_desc);

  // configure Dear ImGui with our own embedded font
  ImGuiIO *io = igGetIO();
  ImFontConfig fontCfg = {};
  fontCfg.FontDataOwnedByAtlas = false;
  fontCfg.OversampleH = 2;
  fontCfg.OversampleV = 2;
  fontCfg.RasterizerMultiply = 1.5f;
  ImFontAtlas_AddFontFromMemoryTTF(io->Fonts, dump_font, sizeof(dump_font),
                                   16.0f, &fontCfg, NULL);

  // create font texture and linear-filtering sampler for the custom font
  // NOTE: linear filtering looks better on low-dpi displays, while
  // nearest-filtering looks better on high-dpi displays
  simgui_font_tex_desc_t font_texture_desc = {};
  font_texture_desc.min_filter = SG_FILTER_LINEAR;
  font_texture_desc.mag_filter = SG_FILTER_LINEAR;
  simgui_create_fonts_texture(&font_texture_desc);

  // initial clear color
  state.pass_action =
      (sg_pass_action){.colors[0] = {.load_action = SG_LOADACTION_CLEAR,
                                     .clear_value = {0.0f, 0.5f, 1.0f, 1.0}}};
}

static void frame(void) {
  simgui_new_frame(&(simgui_frame_desc_t){
      .width = sapp_width(),
      .height = sapp_height(),
      .delta_time = sapp_frame_duration(),
      .dpi_scale = sapp_dpi_scale(),
  });

  /*=== UI CODE STARTS HERE ===*/
  igSetNextWindowPos((ImVec2){10, 10}, ImGuiCond_Once);
  igSetNextWindowSize((ImVec2){400, 100}, ImGuiCond_Once);
  igBegin("Hello Dear ImGui!", 0, ImGuiWindowFlags_None);
  igColorEdit3("Background", &state.pass_action.colors[0].clear_value.r,
               ImGuiColorEditFlags_None);
  igShowMetricsWindow(NULL);
  igEnd();
  /*=== UI CODE ENDS HERE ===*/

  sg_begin_pass(
      &(sg_pass){.action = state.pass_action, .swapchain = sglue_swapchain()});
  simgui_render();
  sg_end_pass();
  sg_commit();
}

static void cleanup(void) {
  simgui_shutdown();
  sg_shutdown();
}

static void event(const sapp_event *ev) { simgui_handle_event(ev); }

sapp_desc sokol_main(int argc, char *argv[]) {
  (void)argc;
  (void)argv;
  return (sapp_desc){
      .init_cb = init,
      .frame_cb = frame,
      .cleanup_cb = cleanup,
      .event_cb = event,
      .window_title = "Hello Sokol + Dear ImGui",
      .width = 800,
      .height = 600,
      .fullscreen = true,
      .high_dpi = true,
      .icon.sokol_default = true,
      .logger.func = slog_func,
  };
}

edit: I cleaned up the fontCfg struct a little

[floooh]

I could reproduce the issue but also was able to fix it... it looks like the cimgui C-API wrapper doesn't properly initialize default values in the ImFontCfg struct, so you'll have to explicitly provide a couple of additional values which are not needed in the C++ API (and you can also use C99 designated init which looks a bit nicer):

    simgui_setup(&(simgui_desc_t){
        .no_default_font = true,
        .logger.func = slog_func,
    });

    ImFontConfig fontCfg = {
        .FontDataOwnedByAtlas = false,
        .OversampleH = 2,
        .OversampleV = 2,
        .GlyphMaxAdvanceX = 1024.0f,    // some arbitrary big value
        .RasterizerMultiply = 1.5f,
        .RasterizerDensity = 1.0f,
    };
    ImFontAtlas_AddFontFromMemoryTTF(igGetIO()->Fonts, dump_font, sizeof(dump_font), 16.0f, &fontCfg, 0);

    simgui_create_fonts_texture(&(simgui_font_tex_desc_t){
        .min_filter = SG_FILTER_LINEAR,
        .mag_filter = SG_FILTER_LINEAR,
    });

The important changes are in the ImFontConfig. For a nicer quality you should also set .high_dpi = true, down in sokol_main. With those changes I get:

[sadguitarius]

Fantastic! Thank you so much. I'll keep that in mind when using cimgui and check default values in the C++ API. I was getting a crash using designated initializers before the proper default values were in there, so I thought that was breaking things somehow. Anyway, thank you!

[sonoro1234]

it looks like the cimgui C-API wrapper doesn't properly initialize default values in the ImFontCfg struct

You can create an ImFontConfig* which is correctly initialized with ImFontConfig_ImFontConfig()
Please give me some feedback on the next issue

[sadguitarius]

I think I may have been a little mixed up here, but cimgui in this repo is generated in a different manner than the cimgui here right? I'm new to this library and trying to follow the trail of the different bindings. Apologies to all who I may have confused in my own confusion.

[floooh]

Yes the Dear ImGui bindings used in the cimgiui-sokol-starterkit repo are generated with the Dear ImGui approach. I just used the 'ig' prefix and the cimgui library name so I only had to change the few differences between the original cimgui bindings and the Dear ImGui bindings.

[sadguitarius]

Got it! And so relating to the missing constructor in this repository, I guess this is a whole thing with dearbindings. I understand things are changing quickly so I'll try not to annoy people any further while I'm figuring this stuff out. Thanks!