ImGui+OpenGL, render function can't render fonts [closed] - c++

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As the title says, I am using ImGui and I can't get my render function to render the fonts.
Things I have done:
Verified my texture is loaded properly with RenderDoc
Verified that my vertex attribute pointers are compliant with ImGui's convention (array of structs).
Below is my rendering code. You can also see the developer's example code for OpenGL here: https://github.com/ocornut/imgui/blob/master/examples/opengl3_example/imgui_impl_glfw_gl3.cpp
// Setup some GL state
glEnable(GL_BLEND);
glBlendEquation(GL_FUNC_ADD);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glDisable(GL_CULL_FACE);
glDisable(GL_DEPTH_TEST);
glEnable(GL_SCISSOR_TEST);
glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
// Setup orthographic projection
glViewport(0, 0, (GLsizei)fb_width, (GLsizei)fb_height);
const float ortho_projection[4][4] =
{
{ 2.0f/io.DisplaySize.x, 0.0f, 0.0f, 0.0f },
{ 0.0f, 2.0f/-io.DisplaySize.y, 0.0f, 0.0f },
{ 0.0f, 0.0f, -1.0f, 0.0f },
{-1.0f, 1.0f, 0.0f, 1.0f },
};
// Setup the shader. bind() calls glUseProgram and enables/disables the proper vertex attributes
shadeTextured->bind();
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, g_FontTexture);
shadeTextured->setUniformM4(Shader::uhi_transform, *(glm::mat4*)&ortho_projection[0][0]);
shadeTextured->setUniformSampler(1, 0);
// Set my vertex attribute pointers for position and tex coords
glVertexAttribPointer(0,
2,
GL_FLOAT,
GL_FALSE,
sizeof(ImDrawVert),
(GLvoid*)IM_OFFSETOF(ImDrawVert, pos));
glVertexAttribPointer(1,
2,
GL_FLOAT,
GL_FALSE,
sizeof(ImDrawVert),
(GLvoid*)IM_OFFSETOF(ImDrawVert, uv));
// Loop through all commands ImGui has
for (int n = 0; n < draw_data->CmdListsCount; n++) {
const ImDrawList* cmd_list = draw_data->CmdLists[n];
const ImDrawIdx* idx_buffer_offset = 0;
glBindBuffer(GL_ARRAY_BUFFER, g_VboHandle);
glBufferData(GL_ARRAY_BUFFER,
(GLsizeiptr)cmd_list->VtxBuffer.Size * sizeof(ImDrawVert),
(const GLvoid*)cmd_list->VtxBuffer.Data,
GL_STREAM_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, g_ElementsHandle);
glBufferData(GL_ELEMENT_ARRAY_BUFFER,
(GLsizeiptr)cmd_list->IdxBuffer.Size * sizeof(ImDrawIdx),
(const GLvoid*)cmd_list->IdxBuffer.Data,
GL_STREAM_DRAW);
for (int cmd_i = 0; cmd_i < cmd_list->CmdBuffer.Size; cmd_i++) {
const ImDrawCmd* pcmd = &cmd_list->CmdBuffer[cmd_i];
glScissor((int)pcmd->ClipRect.x,
(int)(fb_height - pcmd->ClipRect.w),
(int)(pcmd->ClipRect.z - pcmd->ClipRect.x),
(int)(pcmd->ClipRect.w - pcmd->ClipRect.y));
glDrawElements(GL_TRIANGLES,
(GLsizei)pcmd->ElemCount,
sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT,
idx_buffer_offset);
idx_buffer_offset += pcmd->ElemCount;
}
}
And here are the (very, very simple) shaders I have written. The shaders have worked texturing a button before, so I am assuming they are functionally correct.
Vertex shader:
#version 330 core
layout (location = 0) in vec2 pos;
layout (location = 1) in vec2 texCoord;
out vec2 fragTexCoord;
uniform mat4 transform;
void main() {
gl_Position = transform * vec4(pos, 0.0, 1.0);
fragTexCoord = texCoord;
}
Fragment shader:
#version 330 core
out vec4 fragColor;
in vec2 fragTexCoord;
uniform sampler2D sampler;
void main() {
fragColor = texture(sampler, fragTexCoord);
}
I'm at a total loss! Any help would be greatly appreciated

Answer 1

Debugging an incorrect OpenGL setup/state can be quite difficult. It's unclear why you are not using exactly the code provided in imgui_impl_glfw_gl3.cpp and rewriting your own, but what you may do is:
Start again from the supposedly working imgui_impl_glfw_gl3.cpp and turn it step by step into your own and see what makes it break?
Disable scissor temporarily.
Since you are using RenderDoc already: does it show you the correct mesh? Are the vertices that it shows you ok?