Render State section

Image-Loading-and-Displaying-Examples.md

@@ -12,6 +12,8 @@
 - [Example for Vulkan users](#example-for-vulkan-users)
 - [Example for WebGPU users](#example-for-webgpu-users)
 - [About Texture Coordinates](#about-texture-coordinates)
+- [Modifying Render State](#modifying-render-state)
+
 
 ## TL;DR;
 
@@ -1140,4 +1142,49 @@ ImGui::Image((void*)(intptr_t)my_image_texture, ImVec2(my_image_width*0.5f, my_i
 
 ![Scaled](https://user-images.githubusercontent.com/8225057/79073856-25b40380-7ce9-11ea-91e4-754c3232fb58.png)
 
+----
+
+## Modifying Render State
+
+You can use draw callbacks to manipulate the render state, e.g. alter sampling. Since 1.91.3, backends are now exposing some of their state during the render loop, which should make it easier to leverage callbacks. Refer to the .h file of each backend to see if a `ImGui_ImplXXXX_RenderState` struct is exposed.
+<BR>Access them with e.g. `ImGui_ImplDX11_RenderState* state = (ImGui_ImplDX11_RenderState*)ImGui::GetPlatformIO().Renderer_RenderState;`.
+
+```cpp
+// For DX11 backend: Callback to modify current sampler
+void ImDrawCallback_ImplDX11_SetSampler(const ImDrawList* parent_list, const ImDrawCmd* cmd)
+{
+    ImGui_ImplDX11_RenderState* state = (ImGui_ImplDX11_RenderState*)ImGui::GetPlatformIO().Renderer_RenderState;
+    ID3D11SamplerState* sampler = cmd->UserCallbackData ? (ID3D11SamplerState*)cmd->UserCallbackData : state->SamplerDefault;
+    state->DeviceContext->PSSetSamplers(0, 1, &sampler);
+}
+```
+
+```cpp
+// For DX11 backend: Create a Point sampler    
+{
+    D3D11_SAMPLER_DESC desc;
+    ZeroMemory(&desc, sizeof(desc));
+    desc.Filter = D3D11_FILTER_MIN_MAG_MIP_POINT;
+    desc.AddressU = D3D11_TEXTURE_ADDRESS_WRAP;
+    desc.AddressV = D3D11_TEXTURE_ADDRESS_WRAP;
+    desc.AddressW = D3D11_TEXTURE_ADDRESS_WRAP;
+    desc.MipLODBias = 0.f;
+    desc.ComparisonFunc = D3D11_COMPARISON_ALWAYS;
+    desc.MinLOD = 0.f;
+    desc.MaxLOD = 0.f;
+    g_pd3dDevice->CreateSamplerState(&desc, &g_SamplerPoint);
+}
+```
+
+```cpp
+// Usage
+ImGui::GetWindowDrawList()->AddCallback(ImDrawCallback_ImplDX11_SetSampler, g_SamplerPoint); // Set custom sampler
+ImGui::Image((void*)my_texture, ImVec2((float)my_image_width * 4, (float)my_image_height * 4));
+ImGui::GetWindowDrawList()->AddCallback(ImDrawCallback_ImplDX11_SetSampler, NULL); // Restore sampler
+```
+
+This may be easier ot harder to use for some backends. Don't hesitate to open issues to discuss your needs and so we can improve the feature.
+
+----
+
 ##### [Return to Index](#index)