OpenGL imgui slider ranges - c++

Question

I have a 960x540 window I'm creating using OpenGL. Rendering one texture here and using imgui to implement a slider that let's me translate the x, y, and z positions at runtime.
int window_width = 960;
int window_height = 540;
window = glfwCreateWindow(window_width, window_height, "Object Oriented OpenGL", NULL, NULL);
First I set the slider default values.
glm::vec3 model_matrix_translation(200, 200, 0);
Later in my loop that renders the objects positions frame by frame as long as the window is open, I set the ImGui::SliderFloat3 v_min and v_max params to be the dimensions of my window. It appears all 3 sliders x,y, and z use these values, but is there a way to set a range for each individuals slider? As you can see my slider for the y axis can go beyond 540.
while (!glfwWindowShouldClose(window))
{
// renderer and other code before this point
{
ImGui::SliderFloat3("Model Matrix Translation", &model_matrix_translation.x, 0.0f, 960.0f);
}
ImGui::Render();
ImGui_ImplGlfwGL3_RenderDrawData(ImGui::GetDrawData());
glfwSwapBuffers(window);
glfwPollEvents();
}

Answer 1

The implementation of SliderFloat3 delegates to SliderScalarN, which is implemented as such:
bool ImGui::SliderScalarN(const char* label, ImGuiDataType data_type, void* v, int components, const void* v_min, const void* v_max, const char* format, float power)
{
ImGuiWindow* window = GetCurrentWindow();
if (window->SkipItems)
return false;
ImGuiContext& g = *GImGui;
bool value_changed = false;
BeginGroup();
PushID(label);
PushMultiItemsWidths(components, CalcItemWidth());
size_t type_size = GDataTypeInfo[data_type].Size;
for (int i = 0; i < components; i++)
{
PushID(i);
if (i > 0)
SameLine(0, g.Style.ItemInnerSpacing.x);
value_changed |= SliderScalar("", data_type, v, v_min, v_max, format, power);
PopID();
PopItemWidth();
v = (void*)((char*)v + type_size);
}
PopID();
const char* label_end = FindRenderedTextEnd(label);
if (label != label_end)
{
SameLine(0, g.Style.ItemInnerSpacing.x);
TextEx(label, label_end);
}
EndGroup();
return value_changed;
}
For your purposes, you will need to use a modified version of this function that moves v_min and v_max along with v, so in your modified function, change the last line of that for loop to:
v = (void*)((char*)v + type_size);
v_min = (void*)((char*)v_min + type_size);
v_max = (void*)((char*)v_max + type_size);
Or just specialize the whole function to take float* instead and then you can just do v++, v_min++, v_max++; instead.
Finally, you can call your modified function as follows:
float mins[] = {0.0f, 0.0f, 0.0f};
float maxs[] = {960.0f, 540.0f, 0.0f};
MyModifiedSliderFloat3("Model Matrix Translation", &model_matrix_translation.x, mins, maxs);