Why the text show like cube


Version/Branch of Dear ImGui:
Back-end file/Renderer/OS:
glfw + opengl2 + imgui

My Issue/Question:
why the text show like the attachment?
when I use this code,it’s show text like cube:
ImGui::GetIO().Fonts->AddFontFromFileTTF(“msyh.ttc”, 60.0f, NULL, ImGui::GetIO().Fonts->GetGlyphRangesChineseFull());

but I use this code,it’s show text like normal:
ImGui::GetIO().Fonts->AddFontFromFileTTF(“msyh.ttc”, 60.0f, NULL, ImGui::GetIO().Fonts->GetGlyphRangesChineseSimplifiedCommon());



This happen if you failed to upload the texture to the GPU, which generally happen if the texture is too small.
GetGlyphRangesChineseFull() at size 60 with Oversampling bigger than 1 is going to create way too large textures.

Please read misc/fonts/README (https://github.com/ocornut/imgui/tree/master/misc/fonts)
In particular I have just updated this section:

 If you have very large number of glyphs or multiple fonts, the texture may become too big for your graphics API.
 The typical result of failing to upload a texture is if every glyphs appears as white rectangles.
 In particular, using a large range such as GetGlyphRangesChineseSimplifiedCommon() is not recommended unless you 
 set OversampleH/OversampleV to 1 and use a small font size.
 Mind the fact that some graphics drivers have texture size limitation.
 If you are building a PC application, mind the fact that your users may use hardware with lower limitations than yours.
 Some solutions:

  - 1) Reduce glyphs ranges by calculating them from source localization data. You can use ImFont::GlyphRangesBuilder for this purpose,
    this will be the biggest win. 
  - 2) You may reduce oversampling, e.g. config.OversampleH = config.OversampleV = 1, this will largely reduce your texture size.
  - 3) Set io.Fonts.TexDesiredWidth to specify a texture width to minimize texture height (see comment in ImFontAtlas::Build function).
  - 4) Set io.Fonts.Flags |= ImFontAtlasFlags_NoPowerOfTwoHeight; to disable rounding the texture height to the next power of two.