Fixup Save/LoadLastRunWindowBounds: also save DpiWindowSizeFactor / r…

…estore size with DPI handling

src/hello_imgui/internal/backend_impls/abstract_runner.cpp

@@ -159,6 +159,39 @@ void AbstractRunner::PrepareWindowGeometry()
     params.appWindowParams.windowGeometry.size = windowBounds.size;
 }
 
+
+// If needed, change the size to match the current DPI versus the DPI when the size was saved
+// (we want the window to "look" as big as it was when saved, even if the DPI has changed,
+//  or if we are on a different monitor / computer / OS)
+void AbstractRunner::AdjustWindowBoundsAfterCreation_IfDpiChangedBetweenRuns()
+{
+    bool reloadLastSize = params.appWindowParams.restorePreviousGeometry &&
+                          HelloImGuiIniSettings::LoadLastRunWindowBounds(IniSettingsLocation(params)).has_value();
+    if (!reloadLastSize)
+        return;
+
+    std::optional<float> lastRunDpiWindowSizeFactorOpt = HelloImGuiIniSettings::LoadLastRunDpiWindowSizeFactor(IniSettingsLocation(params));
+    if (!lastRunDpiWindowSizeFactorOpt.has_value())
+        return;
+
+    float lastRunDpiWindowSizeFactor = lastRunDpiWindowSizeFactorOpt.value();
+    float currentDpiWindowSizeFactor = params.dpiAwareParams.dpiWindowSizeFactor;
+    float ratio = currentDpiWindowSizeFactor / lastRunDpiWindowSizeFactor;
+    bool isSane = ratio > 0.25f && ratio < 4.f;
+    if (isSane && ratio != 1.f)
+    {
+        auto bounds = mBackendWindowHelper->GetWindowBounds(mWindow);
+        bounds.size = {(int)((float)bounds.size[0] * ratio),
+                       (int)((float)bounds.size[1] * ratio)};
+        bounds.position = {
+            (int)((float)bounds.position[0] * ratio),
+            (int)((float)bounds.position[1] * ratio)
+        };
+        mBackendWindowHelper->SetWindowBounds(mWindow, bounds);
+    }
+}
+
+
 bool AbstractRunner::WantAutoSize()
 {
 #ifdef __EMSCRIPTEN__
@@ -717,6 +750,7 @@ void AbstractRunner::Setup()
             //printf("Window resized by code\n");
         }
     };
+
     Impl_CreateWindow(fnRenderCallbackDuringResize);
 
     #ifdef HELLOIMGUI_HAS_OPENGL
@@ -729,7 +763,10 @@ void AbstractRunner::Setup()
 
     Impl_SetWindowIcon();
 
+    // The order is important: first read the DPI aware params
     SetupDpiAwareParams();
+    // Then adjust window size if needed
+    AdjustWindowBoundsAfterCreation_IfDpiChangedBetweenRuns();
 
 
     // This should be done before Impl_LinkPlatformAndRenderBackends()

src/hello_imgui/internal/backend_impls/abstract_runner.h

@@ -90,6 +90,7 @@ class AbstractRunner
     void SetupDpiAwareParams();
     bool CheckDpiAwareParamsChanges();
     void PrepareWindowGeometry();
+    void AdjustWindowBoundsAfterCreation_IfDpiChangedBetweenRuns();
     void HandleDpiOnSecondFrame();
     void MakeWindowSizeRelativeTo96Ppi_IfRequired();
     bool ShallSizeWindowRelativeTo96Ppi();

src/hello_imgui/internal/hello_imgui_ini_settings.cpp

@@ -193,7 +193,6 @@ namespace HelloImGui
             if (!iniParts.HasIniPart("AppWindow"))
                 return std::nullopt;
 
-
             auto iniPartContent = iniParts.GetIniPart("AppWindow");
             ini::IniFile iniFile;
             try
@@ -235,50 +234,51 @@ namespace HelloImGui
                     failed = true;
             }
 
-            // Read DPI Window Size Factor
-            // If needed, change the size to match the current DPI versus the DPI when the size was saved
-            // (we want the window to "look" as big as it was when saved, even if the DPI has changed,
-            //  or if we are on a different monitor / computer / OS)
+            if (failed)
+                return std::nullopt;
+            else
+                return screenBounds;
+
+        }
+
+        std::optional<float> LoadLastRunDpiWindowSizeFactor(const std::string& iniPartsFilename)
+        {
+            IniParts iniParts = IniParts::LoadFromFile(iniPartsFilename);
+
+            if (!iniParts.HasIniPart("AppWindow"))
+                return std::nullopt;
+
+            auto iniPartContent = iniParts.GetIniPart("AppWindow");
+            ini::IniFile iniFile;
+            try
             {
-                // DpiWindowSizeFactor was added late, so it may not be present in the ini file
-                if (appWindowSection.find("DpiWindowSizeFactor") != appWindowSection.end())
-                {
-                    float dpiWindowSizeFactor_Now =
-                        HelloImGui::GetRunnerParams()->dpiAwareParams.dpiWindowSizeFactor;
-                    float dpiWindowSizeFactor_WhenSaved =
-                        iniFile["AppWindow"]["DpiWindowSizeFactor"].as<float>();
-                    bool isDpiSane = (dpiWindowSizeFactor_WhenSaved >= 0.1f) &&
-                                     (dpiWindowSizeFactor_WhenSaved <= 10.f) &&
-                                     (dpiWindowSizeFactor_Now > 0.1f) && 
-                                     (dpiWindowSizeFactor_Now < 10.f);
-                    if (isDpiSane)
-                    {
-                        float ratio = dpiWindowSizeFactor_Now / dpiWindowSizeFactor_WhenSaved;
-                        if (ratio != 1.f)
-                        {
-                            auto applyRatio = [](int v, float ratio) -> int
-                            {
-                                return static_cast<int>(static_cast<float>(v) * ratio);
-                            };
-                            screenBounds.position[0] = applyRatio(screenBounds.position[0], ratio);
-                            screenBounds.position[1] = applyRatio(screenBounds.position[1], ratio);
-                            screenBounds.size[0] = applyRatio(screenBounds.size[0], ratio);
-                            screenBounds.size[1] = applyRatio(screenBounds.size[1], ratio);
-                        }
-                    }
-                }
+                iniFile.decode(iniPartContent);
             }
+            catch (const std::exception &)
             {
-
+                return std::nullopt;
             }
 
-            if (failed)
+            ScreenBounds screenBounds;
+            bool failed = false;
+
+            if (iniFile.find("AppWindow") == iniFile.end())
                 return std::nullopt;
-            else
-                return screenBounds;
+            auto &appWindowSection = iniFile["AppWindow"];
 
+            if (appWindowSection.find("DpiWindowSizeFactor") != appWindowSection.end())
+            {
+                float dpiWindowSizeFactor_WhenSaved =
+                    iniFile["AppWindow"]["DpiWindowSizeFactor"].as<float>();
+                bool isDpiSane = (dpiWindowSizeFactor_WhenSaved >= 0.1f) &&
+                                 (dpiWindowSizeFactor_WhenSaved <= 10.f);
+                if (isDpiSane)
+                    return dpiWindowSizeFactor_WhenSaved;
+            }
+            return std::nullopt;
         }
 
+
         void LoadImGuiSettings(const std::string& iniPartsFilename, const std::string& layoutName)
         {
             std::string iniPartName = "ImGui_" + details::SanitizeIniNameOrCategory(layoutName);

src/hello_imgui/internal/hello_imgui_ini_settings.h

@@ -61,6 +61,7 @@ namespace HelloImGui
         //
         void SaveLastRunWindowBounds(const std::string& iniPartsFilename, const ScreenBounds& windowBounds);
         std::optional<ScreenBounds> LoadLastRunWindowBounds(const std::string& iniPartsFilename);
+        std::optional<float> LoadLastRunDpiWindowSizeFactor(const std::string& iniPartsFilename);
         void SaveHelloImGuiMiscSettings(const std::string& iniPartsFilename, const RunnerParams& runnerParams);
         void LoadHelloImGuiMiscSettings(const std::string& iniPartsFilename, RunnerParams* inOutRunnerParams);