feat(shaders_lab): independent windows for Code, DAG, Controls, Canvas, GLSL

Remove Code/DAG toggle. Each panel lives in its own dockable window.
Active source (Code or DAG) is whichever window has focus; Canvas title
shows the current active source. Switching active source triggers an
immediate recompile so the canvas reflects the selected pipeline.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cpp/apps/shaders_lab/main.cpp

@@ -13,12 +13,14 @@
 #include "seed_shaders.h"
 
 #include <chrono>
+#include <cstdio>
+#include <cstring>
 #include <string>
 #include <vector>
 
-enum class AppMode { Code, Dag };
+enum class Source { Code, Dag };
 
-static AppMode g_mode = AppMode::Code;
+static Source g_active = Source::Code;
 static fn::gfx::ShaderCanvas g_canvas;
 static std::string g_source = PLASMA;
 static std::string g_last_err;
@@ -31,7 +33,7 @@ static std::vector<fn::gfx::DagStep> g_pipeline;
 static std::string g_dag_glsl;
 
 static void try_compile() {
-    if (g_mode == AppMode::Code) {
+    if (g_active == Source::Code) {
         auto r = fn::gfx::compile_fragment(g_source);
         if (r.ok) {
             g_descs = fn::gfx::parse_uniforms(g_source);
@@ -47,8 +49,6 @@ static void try_compile() {
         g_dag_glsl = fn::gfx::compile_dag_to_glsl(g_pipeline);
         auto r = fn::gfx::compile_fragment(g_dag_glsl);
         if (r.ok) {
-            g_descs.clear();
-            g_store.values.clear();
             fn::gfx::canvas_set_program(g_canvas, r.program);
             g_last_err.clear();
             g_last_err_line = -1;
@@ -64,6 +64,13 @@ static void mark_dirty() {
     g_dirty = true;
 }
 
+static void set_active(Source s) {
+    if (g_active != s) {
+        g_active = s;
+        try_compile();
+    }
+}
+
 static void load_preset(const char* src) {
     g_source = src;
     mark_dirty();
@@ -78,11 +85,21 @@ static void ensure_dag_default() {
             step.name   = def->name;
             step.params = def->param_defaults;
             g_pipeline.push_back(step);
-            mark_dirty();
         }
     }
 }
 
+static void draw_err_footer() {
+    if (g_last_err.empty()) return;
+    ImGui::Separator();
+    if (g_last_err_line > 0) {
+        ImGui::TextColored(ImVec4(1, 0.4f, 0.4f, 1), "line %d: %s",
+                           g_last_err_line, g_last_err.c_str());
+    } else {
+        ImGui::TextColored(ImVec4(1, 0.4f, 0.4f, 1), "%s", g_last_err.c_str());
+    }
+}
+
 static void render() {
     if (!g_canvas.initialized) fn::gfx::canvas_init(g_canvas);
 
@@ -97,90 +114,56 @@ static void render() {
 
     ImGui::DockSpaceOverViewport(0, ImGui::GetMainViewport());
 
-    // --- Left panel: Code or DAG ---
+    // --- Code window ---
-    const char* panel_title = (g_mode == AppMode::Code) ? "Code" : "DAG";
+    if (ImGui::Begin("Code")) {
-    if (ImGui::Begin(panel_title)) {
+        if (ImGui::IsWindowFocused(ImGuiFocusedFlags_RootAndChildWindows)) {
-        // Mode toggle topbar
+            set_active(Source::Code);
-        {
-            bool code_active = (g_mode == AppMode::Code);
-            bool dag_active  = (g_mode == AppMode::Dag);
-            if (code_active) ImGui::PushStyleColor(ImGuiCol_Button, ImVec4(0.3f, 0.5f, 0.8f, 1.0f));
-            if (ImGui::Button("Code")) {
-                if (g_mode != AppMode::Code) {
-                    g_mode = AppMode::Code;
-                    mark_dirty();
-                }
-            }
-            if (code_active) ImGui::PopStyleColor();
-            ImGui::SameLine();
-            if (dag_active) ImGui::PushStyleColor(ImGuiCol_Button, ImVec4(0.3f, 0.5f, 0.8f, 1.0f));
-            if (ImGui::Button("DAG")) {
-                if (g_mode != AppMode::Dag) {
-                    g_mode = AppMode::Dag;
-                    ensure_dag_default();
-                    mark_dirty();
-                }
-            }
-            if (dag_active) ImGui::PopStyleColor();
-            ImGui::Separator();
         }
 
-        if (g_mode == AppMode::Code) {
+        if (ImGui::Button("Plasma"))  { load_preset(PLASMA); }
-            if (ImGui::Button("Plasma"))  { load_preset(PLASMA); }
+        ImGui::SameLine();
-            ImGui::SameLine();
+        if (ImGui::Button("Circle"))  { load_preset(CIRCLE); }
-            if (ImGui::Button("Circle"))  { load_preset(CIRCLE); }
+        ImGui::SameLine();
-            ImGui::SameLine();
+        if (ImGui::Button("Checker")) { load_preset(CHECKER); }
-            if (ImGui::Button("Checker")) { load_preset(CHECKER); }
 
-            ImVec2 avail = ImGui::GetContentRegionAvail();
+        bool has_err_here = !g_last_err.empty() && g_active == Source::Code;
-            float footer_height = g_last_err.empty() ? 0.0f : ImGui::GetTextLineHeightWithSpacing() + 8.0f;
+        ImVec2 avail = ImGui::GetContentRegionAvail();
-            ImVec2 editor_size(avail.x, avail.y - footer_height);
+        float footer_height = has_err_here ? ImGui::GetTextLineHeightWithSpacing() + 8.0f : 0.0f;
+        ImVec2 editor_size(avail.x, avail.y - footer_height);
 
-            char buf[1 << 16];
+        char buf[1 << 16];
-            size_t copy_len = g_source.size() < sizeof(buf) - 1 ? g_source.size() : sizeof(buf) - 1;
+        size_t copy_len = g_source.size() < sizeof(buf) - 1 ? g_source.size() : sizeof(buf) - 1;
-            memcpy(buf, g_source.c_str(), copy_len);
+        memcpy(buf, g_source.c_str(), copy_len);
-            buf[copy_len] = '\0';
+        buf[copy_len] = '\0';
 
-            ImGui::PushFont(nullptr);
+        if (ImGui::InputTextMultiline("##code", buf, sizeof(buf), editor_size,
-            if (ImGui::InputTextMultiline("##code", buf, sizeof(buf), editor_size,
+                                      ImGuiInputTextFlags_AllowTabInput)) {
-                                          ImGuiInputTextFlags_AllowTabInput)) {
+            g_source = buf;
-                g_source = buf;
+            mark_dirty();
-                mark_dirty();
-            }
-            ImGui::PopFont();
-
-            if (!g_last_err.empty()) {
-                ImGui::Separator();
-                if (g_last_err_line > 0) {
-                    ImGui::TextColored(ImVec4(1, 0.4f, 0.4f, 1), "line %d: %s",
-                                       g_last_err_line, g_last_err.c_str());
-                } else {
-                    ImGui::TextColored(ImVec4(1, 0.4f, 0.4f, 1), "%s", g_last_err.c_str());
-                }
-            }
-        } else {
-            // DAG mode
-            bool topo_changed = fn::gfx::dag_panel(g_pipeline);
-            if (topo_changed) {
-                mark_dirty();
-            }
-
-            if (!g_last_err.empty()) {
-                ImGui::Separator();
-                if (g_last_err_line > 0) {
-                    ImGui::TextColored(ImVec4(1, 0.4f, 0.4f, 1), "line %d: %s",
-                                       g_last_err_line, g_last_err.c_str());
-                } else {
-                    ImGui::TextColored(ImVec4(1, 0.4f, 0.4f, 1), "%s", g_last_err.c_str());
-                }
-            }
         }
+
+        if (has_err_here) draw_err_footer();
     }
     ImGui::End();
 
-    // --- Canvas panel ---
+    // --- DAG Pipeline window ---
-    if (ImGui::Begin("Canvas")) {
+    if (ImGui::Begin("DAG Pipeline")) {
-        if (g_mode == AppMode::Code) {
+        if (ImGui::IsWindowFocused(ImGuiFocusedFlags_RootAndChildWindows)) {
+            set_active(Source::Dag);
+        }
+        bool topo_changed = fn::gfx::dag_panel(g_pipeline);
+        if (topo_changed) mark_dirty();
+
+        if (!g_last_err.empty() && g_active == Source::Dag) draw_err_footer();
+    }
+    ImGui::End();
+
+    // --- Canvas window ---
+    char canvas_title[64];
+    snprintf(canvas_title, sizeof(canvas_title), "Canvas [%s]###canvas",
+             g_active == Source::Code ? "Code" : "DAG");
+    if (ImGui::Begin(canvas_title)) {
+        if (g_active == Source::Code) {
             fn::gfx::canvas_render(g_canvas, static_cast<float>(ImGui::GetTime()),
                 [](unsigned int program) {
                     fn::gfx::uniforms_apply(g_store, g_descs, program);
@@ -194,28 +177,37 @@ static void render() {
     }
     ImGui::End();
 
-    // --- Controls panel ---
+    // --- Controls window (Code uniforms) ---
     if (ImGui::Begin("Controls")) {
-        if (g_mode == AppMode::Code) {
+        if (g_descs.empty()) {
-            fn::gfx::uniforms_panel(g_store, g_descs);
+            ImGui::TextDisabled("No uniforms declared in Code.");
+            ImGui::TextDisabled("Use // @slider, @color, @toggle, @xy annotations.");
         } else {
-            // Show generated GLSL read-only
+            fn::gfx::uniforms_panel(g_store, g_descs);
-            if (ImGui::CollapsingHeader("Generated GLSL")) {
-                ImVec2 avail = ImGui::GetContentRegionAvail();
-                ImGui::InputTextMultiline("##dag_glsl",
-                    const_cast<char*>(g_dag_glsl.c_str()),
-                    g_dag_glsl.size() + 1,
-                    ImVec2(avail.x, std::min(avail.y, 400.0f)),
-                    ImGuiInputTextFlags_ReadOnly);
-            }
         }
         ImGui::Spacing();
         fps_overlay();
     }
     ImGui::End();
+
+    // --- Generated GLSL window (DAG compiled output, read-only) ---
+    if (ImGui::Begin("Generated GLSL")) {
+        if (g_dag_glsl.empty()) {
+            ImGui::TextDisabled("(DAG not compiled yet — focus the DAG Pipeline window)");
+        } else {
+            ImVec2 avail = ImGui::GetContentRegionAvail();
+            ImGui::InputTextMultiline("##dag_glsl",
+                const_cast<char*>(g_dag_glsl.c_str()),
+                g_dag_glsl.size() + 1,
+                avail,
+                ImGuiInputTextFlags_ReadOnly);
+        }
+    }
+    ImGui::End();
 }
 
 int main() {
+    ensure_dag_default();
     fn::AppConfig cfg;
     cfg.title  = "shaders_lab";
     cfg.width  = 1400;