From 4ce0ee2011c23dc670f8842c76e7c7eacfab7daf Mon Sep 17 00:00:00 2001
From: Haroon Qureshi <haroonq@google.com>
Date: Wed, 26 Nov 2025 02:35:09 -0800
Subject: [PATCH] Update texture handling due to recent ImGui upgrade.

PiperOrigin-RevId: 837030453
Change-Id: I042c4a7df7dc6c7e07c40eb5f32e5031e5b1d60a
---
 .../filament/filament/gui_view.cc             | 64 ++++++++++++++++---
 src/experimental/filament/filament/gui_view.h |  4 +-
 2 files changed, 57 insertions(+), 11 deletions(-)

diff --git a/src/experimental/filament/filament/gui_view.cc b/src/experimental/filament/filament/gui_view.cc
index 2fa5cf53..b331a7b5 100644
--- a/src/experimental/filament/filament/gui_view.cc
+++ b/src/experimental/filament/filament/gui_view.cc
@@ -17,6 +17,7 @@
 #include <cstddef>
 #include <cstdint>
 #include <cstring>
+#include <utility>
 #include <vector>
 
 #include <imgui.h>
@@ -50,15 +51,6 @@ GuiView::GuiView(filament::Engine* engine, ObjectManager* object_mgr)
   view_->setPostProcessingEnabled(false);
 
   material_ = object_mgr_->GetMaterial(ObjectManager::kUnlitUi);
-
-  // Upload the ImGui font as a texture that is sampled by the UX material.
-  int font_width = 0;
-  int font_height = 0;
-  int font_bpp = 0;
-  unsigned char* pixels = nullptr;
-  ImGuiIO& io = ImGui::GetIO();
-  io.Fonts->GetTexDataAsRGBA32(&pixels, &font_width, &font_height, &font_bpp);
-  object_mgr_->UploadFont(pixels, font_width, font_height, 0);
 }
 
 GuiView::~GuiView() {
@@ -88,6 +80,52 @@ void GuiView::ResetRenderable() {
   buffers_.clear();
 }
 
+void GuiView::ProcessTexture(ImTextureData* data) {
+  filament::Engine* engine = object_mgr_->GetEngine();
+
+  if (data->Status == ImTextureStatus_OK) {
+    return;
+  } else if (data->Status == ImTextureStatus_WantCreate) {
+    if (data->Format != ImTextureFormat_RGBA32) {
+      mju_error("Unsupported texture format.");
+    }
+
+    filament::Texture* texture =
+        filament::Texture::Builder()
+            .width(data->Width)
+            .height(data->Height)
+            .levels(1)
+            .format(filament::Texture::InternalFormat::RGBA8)
+            .sampler(filament::Texture::Sampler::SAMPLER_2D)
+            .build(*engine);
+
+    const int size = data->Width * data->Height * 4;
+    filament::Texture::PixelBufferDescriptor pb(data->GetPixels(), size,
+                                                filament::Texture::Format::RGBA,
+                                                filament::Texture::Type::UBYTE);
+    texture->setImage(*engine, 0, std::move(pb));
+
+    data->SetTexID((ImTextureID)texture);
+    data->SetStatus(ImTextureStatus_OK);
+  } else if (data->Status == ImTextureStatus_WantUpdates) {
+    const int size = data->Width * data->Height * 4;
+    filament::Texture::PixelBufferDescriptor pb(data->GetPixels(), size,
+                                                filament::Texture::Format::RGBA,
+                                                filament::Texture::Type::UBYTE);
+    filament::Texture* texture = (filament::Texture*)data->TexID;
+    texture->setImage(*engine, 0, std::move(pb));
+    data->SetStatus(ImTextureStatus_OK);
+  } else if (data->Status == ImTextureStatus_WantDestroy &&
+             data->UnusedFrames > 0) {
+    filament::Texture* texture =
+        reinterpret_cast<filament::Texture*>(data->TexID);
+    engine->destroy(texture);
+
+    data->SetTexID(ImTextureID_Invalid);
+    data->SetStatus(ImTextureStatus_Destroyed);
+  }
+}
+
 bool GuiView::PrepareRenderable() {
   ResetRenderable();
 
@@ -126,6 +164,12 @@ bool GuiView::PrepareRenderable() {
   builder.boundingBox({{-100, -100, -100}, {100, 100, 100}});
   builder.culling(false);
 
+  if (commands->Textures != nullptr) {
+    for (ImTextureData* tex : *commands->Textures) {
+      ProcessTexture(tex);
+    }
+  }
+
   int drawable_index = 0;
   for (int n = 0; n < commands->CmdListsCount; ++n) {
     const ImDrawList* cmds = commands->CmdLists[n];
@@ -190,7 +234,7 @@ filament::MaterialInstance* GuiView::GetMaterialInstance(int index,
                                                          mjrRect rect,
                                                          intptr_t texture_id) {
   while (index >= instances_.size()) {
-    const filament::Texture* texture = object_mgr_->GetFont(texture_id);
+    const auto* texture = reinterpret_cast<filament::Texture*>(texture_id);
 
     filament::TextureSampler sampler;
     filament::MaterialInstance* instance = material_->createInstance();
diff --git a/src/experimental/filament/filament/gui_view.h b/src/experimental/filament/filament/gui_view.h
index a65ec43e..5e41b17d 100644
--- a/src/experimental/filament/filament/gui_view.h
+++ b/src/experimental/filament/filament/gui_view.h
@@ -16,9 +16,9 @@
 #define MUJOCO_SRC_EXPERIMENTAL_FILAMENT_FILAMENT_GUI_VIEW_H_
 
 #include <cstdint>
-#include <unordered_map>
 #include <vector>
 
+#include <imgui.h>
 #include <filament/Camera.h>
 #include <filament/Engine.h>
 #include <filament/Material.h>
@@ -47,6 +47,8 @@ class GuiView {
   filament::View* PrepareRenderView();
 
  private:
+  void ProcessTexture(ImTextureData* data);
+
   // Returns the filament::MaterialInstance configured to draw into the given
   // scissor rect.
   filament::MaterialInstance* GetMaterialInstance(int index, mjrRect rect,