display logo image on background

file/system_imgui.cc

@@ -1,3 +1,7 @@
+#include <algorithm>
+#include <chrono>
+#include <cmath>
+#include <cstdlib>
 #include <memory>
 #include <string>
 #include <string_view>
@@ -6,6 +10,7 @@
 #include <vector>
 
 #include <imgui.h>
+#include <imgui_internal.h>
 
 #include <yaml-cpp/yaml.h>
 
@@ -108,10 +113,59 @@ class ImGui_ final : public nf7::FileBase,
 
  private:
   nf7::GenericMemento<Data> mem_;
+
+
+  static constexpr size_t kLogoQuads = 4;
+  static size_t CalcLogoQuads(ImVec2 quads[kLogoQuads*4], float a) noexcept;
+
+  void DrawLogo() noexcept;
+  void Dockspace() noexcept;
 };
 
 
 void ImGui_::PostUpdate() noexcept {
+  DrawLogo();
+  Dockspace();
+}
+void ImGui_::UpdateMenu() noexcept {
+  if (ImGui::MenuItem("add workspace")) {
+    size_t i = 0;
+    auto& ds = mem_->dockspaces;
+    for (;; ++i) {
+      const auto name = std::to_string(i);
+      if (ds.end() == std::find(ds.begin(), ds.end(), name)) {
+        ds.push_back(name);
+        mem_.Commit();
+        break;
+      }
+    }
+  }
+}
+
+
+void ImGui_::DrawLogo() noexcept {
+  auto d = ImGui::GetBackgroundDrawList();
+
+  const auto em  = ImGui::GetFontSize();
+  const auto sz  = 6*em;
+  const auto pos = ImGui::GetWindowViewport()->Size / 2.f;
+  const auto c   = ImGui::GetColorU32(ImVec4 {.9f, .9f, .9f, 1.f});
+
+  const auto t = ImGui::GetCurrentContext()->Time;
+  const auto a = std::min(static_cast<float>(t)/2.f, 1.f);
+
+  ImVec2 quads[kLogoQuads*4];
+  const auto n = CalcLogoQuads(quads, a);
+
+  for (size_t i = 0; i < n; ++i) {
+    d->AddQuadFilled(
+        quads[i*4+0]*sz + pos,
+        quads[i*4+1]*sz + pos,
+        quads[i*4+2]*sz + pos,
+        quads[i*4+3]*sz + pos, c);
+  }
+}
+void ImGui_::Dockspace() noexcept {
   const auto em = ImGui::GetFontSize();
 
   ImGui::DockSpaceOverViewport(ImGui::GetMainViewport(), ImGuiDockNodeFlags_PassthruCentralNode);
@@ -144,19 +198,69 @@ void ImGui_::PostUpdate() noexcept {
     mem_.Commit();
   }
 }
-void ImGui_::UpdateMenu() noexcept {
-  if (ImGui::MenuItem("add workspace")) {
-    size_t i = 0;
-    auto& ds = mem_->dockspaces;
-    for (;; ++i) {
-      const auto name = std::to_string(i);
-      if (ds.end() == std::find(ds.begin(), ds.end(), name)) {
-        ds.push_back(name);
-        mem_.Commit();
-        break;
-      }
-    }
-  }
+
+
+size_t ImGui_::CalcLogoQuads(ImVec2 quads[kLogoQuads*4], float a) noexcept {
+  static const ImVec2 kVerts[kLogoQuads*4] = {
+    // upper horizontal
+    {-0.3624801619f, -0.2516071429f},
+    { 0.4942659048f, -0.2516071429f},
+    { 0.4438690476f, -0.1508134952f},
+    {-0.412876981f,  -0.1508134952f},
+
+    // lower horizontal
+    {-0.4506746f,    0.06337304762f},
+    { 0.4060714286f, 0.06337304762f},
+    { 0.3556745714f, 0.1641666667f},
+    {-0.5010714286f, 0.1641666667f},
+
+    // left vertical
+    {-0.1104960286f,  -0.8185714286f},
+    {-0.06009920952f, -0.4720932571f},
+    {-0.2112896857f,   0.9705159048f},
+    {-0.3183829333f,   0.523244f},
+
+    // right vertical
+    {0.1981844762f,  -0.9760615076f},
+    {0.3115773333f,  -0.5854861143f},
+    {0.09739085714f,  0.7374305714f},
+    {0.06589285714f,  0.3405555238f},
+  };
+  std::memcpy(quads, kVerts, sizeof(kVerts));
+
+  a *= 4.f;
+  const auto a1 = std::pow(std::clamp(a-0.f, 0.f, 1.f), 5.f);
+  const auto a2 = std::pow(std::clamp(a-1.f, 0.f, 1.f), 4.f);
+
+# define Linear_(a, b, t)  \
+  quads[i+a] = (quads[i+a]-quads[i+b])*t + quads[i+b]
+
+  // upper horizontal
+  size_t i = 0;
+  Linear_(1, 0, a1);
+  Linear_(2, 3, a1);
+
+  // lower horizontal
+  i += 4;
+  Linear_(0, 1, a1);
+  Linear_(3, 2, a1);
+
+  if (a2 <= 0) return 2;
+
+  // left vertical
+  i += 4;
+  Linear_(1, 0, std::min(a2*4.f, 1.f));
+  Linear_(2, 0, a2);
+  Linear_(3, 0, a2);
+
+  // right vertical
+  i += 4;
+  Linear_(0, 2, a2);
+  Linear_(1, 2, a2);
+  Linear_(3, 2, std::min(a2*4.f, 1.f));
+  return 4;
+
+# undef Linear_
 }
 
 }