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AbstractRunner::CreateFramesAndRender: detach python GIL inside nativ…
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…e code
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@pthom
pthom committed Jan 18, 2024
1 parent 7cfbf93 commit 2449df4
Showing 1 changed file with 177 additions and 100 deletions.
277 changes: 177 additions & 100 deletions src/hello_imgui/internal/backend_impls/abstract_runner.cpp
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#include "imgui_internal.h"

#include "hello_imgui_test_engine_integration/test_engine_integration.h"
#include "imgui_test_engine/imgui_te_python_gil.h"

#ifdef IMGUI_TEST_ENGINE_WITH_PYTHON_GIL
#define SCOPED_RELEASE_GIL_ON_MAIN_THREAD ImGuiTestEnginePythonGIL::ReleaseGilOnMainThread_Scoped _gilRelease
#else
#define SCOPED_RELEASE_GIL_ON_MAIN_THREAD (void)
#endif

#include <chrono>
#include <cassert>
Expand Down Expand Up @@ -495,168 +502,238 @@ void AbstractRunner::RenderGui()

void AbstractRunner::CreateFramesAndRender()
{
LayoutSettings_HandleChanges();
// Notes:
// - this method is rather long, but this is intentional in order to be able to see the logic flow at a glance
// - the code is organized in blocks of code that are enclosed by
// if (true) // Block explanation
// {
// ...
// }
// this enables to limit the scope of each block, and enable to collapses them
// when inside an IDE
// - Some blocks include a SCOPED_RELEASE_GIL_ON_MAIN_THREAD statement, like this:
// if (true_gil) // block explanation (`true_gil` is a synonym for "true")
// { // SCOPED_RELEASE_GIL_ON_MAIN_THREAD start
// SCOPED_RELEASE_GIL_ON_MAIN_THREAD; // SCOPED_RELEASE_GIL_ON_MAIN_THREAD does nothing if not using python
//
// ... // Block logic that is executed *whenever using Python or not*
//
// } // SCOPED_RELEASE_GIL_ON_MAIN_THREAD end
// This means that they will release the Gil for python, and that they should not call
// any user callback (which may call python functions)
// -

#if TARGET_OS_IOS
auto insets = GetIPhoneSafeAreaInsets();
params.appWindowParams.edgeInsets.top = insets.top;
params.appWindowParams.edgeInsets.left = insets.left;
params.appWindowParams.edgeInsets.bottom = insets.bottom;
params.appWindowParams.edgeInsets.right = insets.right;
#endif
// `true_gil` is a synonym for "true" (whenever using Python or not using Python)
// (it is here only to make the code more readable)
constexpr bool true_gil = true;

#ifdef HELLOIMGUI_WITH_TEST_ENGINE
if (mIdxFrame >= 1)
if (true_gil) // basic layout checks
{ // SCOPED_RELEASE_GIL_ON_MAIN_THREAD start
SCOPED_RELEASE_GIL_ON_MAIN_THREAD;


LayoutSettings_HandleChanges();

#if TARGET_OS_IOS
auto insets = GetIPhoneSafeAreaInsets();
params.appWindowParams.edgeInsets.top = insets.top;
params.appWindowParams.edgeInsets.left = insets.left;
params.appWindowParams.edgeInsets.bottom = insets.bottom;
params.appWindowParams.edgeInsets.right = insets.right;
#endif
} // SCOPED_RELEASE_GIL_ON_MAIN_THREAD end

if (true) // Register tests
{
if (params.useImGuiTestEngine && params.callbacks.RegisterTests && (!params.callbacks.registerTestsCalled))
#ifdef HELLOIMGUI_WITH_TEST_ENGINE
// This block calls a user callback, so it cannot be inside SCOPED_RELEASE_GIL_ON_MAIN_THREAD
if (mIdxFrame >= 1)
{
params.callbacks.RegisterTests();
params.callbacks.registerTestsCalled = true;
if (params.useImGuiTestEngine && params.callbacks.RegisterTests && (!params.callbacks.registerTestsCalled))
{
params.callbacks.RegisterTests();
params.callbacks.registerTestsCalled = true;
}
}
#endif
}
#endif

// Note about the application window initial placement and sizing
// i/ On the first frame (mIdxFrame==0), we create a window, and use the user provided size (if provided). The window is initially hidden.
// (this was done much sooner by mBackendWindowHelper)
// ii/ On the second frame (mIdxFrame == 1), we may multiply this size by the Dpi factor (if > 1), to handle windows and linux High DPI
// iii/ At the end of the second frame, we measure the size of the widgets and use it as the application window size, if the user required auto size
// iv/ At the beginning of the third frame (mIdxFrame==2 / mWasWindowAutoResizedOnPreviousFrame), we may apply the auto-size and recenter the window to the center of the monitor
// v/ At the 4th frame (mIdxFrame >= 3), we finally show the window
// Phew...

// ii/ On the second frame (mIdxFrame == 1), we may multiply this size by the Dpi factor (if > 1), to handle windows and linux High DPI
if (mIdxFrame == 1)
{
// We might resize the window on the second frame on window and linux
// (and rescale ImGui style)
HandleDpiOnSecondFrame();
}
if (true_gil) // handle window size and position on first frames
{ // SCOPED_RELEASE_GIL_ON_MAIN_THREAD start
SCOPED_RELEASE_GIL_ON_MAIN_THREAD;

// Note about the application window initial placement and sizing
// i/ On the first frame (mIdxFrame==0), we create a window, and use the user provided size (if provided). The window is initially hidden.
// (this was done much sooner by mBackendWindowHelper)
// ii/ On the second frame (mIdxFrame == 1), we may multiply this size by the Dpi factor (if > 1), to handle windows and linux High DPI
// iii/ At the end of the second frame, we measure the size of the widgets and use it as the application window size, if the user required auto size
// iv/ At the beginning of the third frame (mIdxFrame==2 / mWasWindowAutoResizedOnPreviousFrame), we may apply the auto-size and recenter the window to the center of the monitor
// v/ At the 4th frame (mIdxFrame >= 3), we finally show the window
// Phew...

// ii/ On the second frame (mIdxFrame == 1), we may multiply this size by the Dpi factor (if > 1), to handle windows and linux High DPI
if (mIdxFrame == 1)
{
// We might resize the window on the second frame on window and linux
// (and rescale ImGui style)
HandleDpiOnSecondFrame();
}

// iv/ At the beginning of the third frame (mIdxFrame==2 / mWasWindowAutoResizedOnPreviousFrame), we may apply the auto-size and recenter the window to the center of the monitor
if (mWasWindowAutoResizedOnPreviousFrame)
{
// The window was resized on last frame
// We should now recenter the window if needed and ensure it fits on the monitor
mGeometryHelper->EnsureWindowFitsMonitor(mBackendWindowHelper.get(), mWindow);

// if this is the third frame, and the user wanted a centered window, let's recenter it
// we do this on the third frame (mIdxFrame == 2), since the initial autosize happens on the second
// (see WantAutoSize())
if (params.appWindowParams.windowGeometry.positionMode == HelloImGui::WindowPositionMode::MonitorCenter && (mIdxFrame == 2))
mGeometryHelper->CenterWindowOnMonitor(mBackendWindowHelper.get(), mWindow);

mWasWindowAutoResizedOnPreviousFrame = false;
params.appWindowParams.windowGeometry.resizeAppWindowAtNextFrame = false;
}
// iv/ At the beginning of the third frame (mIdxFrame==2 / mWasWindowAutoResizedOnPreviousFrame), we may apply the auto-size and recenter the window to the center of the monitor
if (mWasWindowAutoResizedOnPreviousFrame)
{
// The window was resized on last frame
// We should now recenter the window if needed and ensure it fits on the monitor
mGeometryHelper->EnsureWindowFitsMonitor(mBackendWindowHelper.get(), mWindow);

// if this is the third frame, and the user wanted a centered window, let's recenter it
// we do this on the third frame (mIdxFrame == 2), since the initial autosize happens on the second
// (see WantAutoSize())
if (params.appWindowParams.windowGeometry.positionMode == HelloImGui::WindowPositionMode::MonitorCenter &&
(mIdxFrame == 2))
mGeometryHelper->CenterWindowOnMonitor(mBackendWindowHelper.get(), mWindow);

mWasWindowAutoResizedOnPreviousFrame = false;
params.appWindowParams.windowGeometry.resizeAppWindowAtNextFrame = false;
}


static bool lastHiddenState = false;
static bool lastHiddenState = false;

// v/ At the 4th frame (mIdxFrame >= 3), we finally show the window
if (mIdxFrame == 3)
{
if (params.appWindowParams.hidden)
mBackendWindowHelper->HideWindow(mWindow);
else
mBackendWindowHelper->ShowWindow(mWindow);
lastHiddenState = params.appWindowParams.hidden;
}
// On subsequent frames, we take into account user modifications of appWindowParams.hidden
if (mIdxFrame > 3)
{
if (params.appWindowParams.hidden != lastHiddenState)
// v/ At the 4th frame (mIdxFrame >= 3), we finally show the window
if (mIdxFrame == 3)
{
lastHiddenState = params.appWindowParams.hidden;
if (params.appWindowParams.hidden)
mBackendWindowHelper->HideWindow(mWindow);
else
mBackendWindowHelper->ShowWindow(mWindow);
lastHiddenState = params.appWindowParams.hidden;
}
}
// On subsequent frames, we take into account user modifications of appWindowParams.hidden
if (mIdxFrame > 3)
{
if (params.appWindowParams.hidden != lastHiddenState)
{
lastHiddenState = params.appWindowParams.hidden;
if (params.appWindowParams.hidden)
mBackendWindowHelper->HideWindow(mWindow);
else
mBackendWindowHelper->ShowWindow(mWindow);
}
}
} // SCOPED_RELEASE_GIL_ON_MAIN_THREAD end

#ifndef __EMSCRIPTEN__
// Idling for non emscripten, where HelloImGui is responsible for the main loop.
// This form of idling will call WaitForEventTimeout(), which may call sleep():
IdleBySleeping();
#endif
if(true_gil) // Handle idling
{ // SCOPED_RELEASE_GIL_ON_MAIN_THREAD start
SCOPED_RELEASE_GIL_ON_MAIN_THREAD;

// Poll Events (this fills GImGui.InputEventsQueue)
Impl_PollEvents();
#ifndef __EMSCRIPTEN__
// Idling for non emscripten, where HelloImGui is responsible for the main loop.
// This form of idling will call WaitForEventTimeout(), which may call sleep():
IdleBySleeping();
#endif

// Poll Events (this fills GImGui.InputEventsQueue)
Impl_PollEvents();

#ifdef __EMSCRIPTEN__
// Idling for emscripten: early exit if idling
// This test should be done after calling Impl_PollEvents() since it checks the event queue for incoming events!
if (ShallIdleThisFrame_Emscripten())
{
mIdxFrame += 1;
return;
}
#endif
} // SCOPED_RELEASE_GIL_ON_MAIN_THREAD end

#ifdef __EMSCRIPTEN__
// Idling for emscripten: early exit if idling
// This test should be done after calling Impl_PollEvents() since it checks the event queue for incoming events!
if (ShallIdleThisFrame_Emscripten())
{
mIdxFrame += 1;
return;
}
#endif

//
// Rendering logic
//
if (params.callbacks.PreNewFrame)
params.callbacks.PreNewFrame();

mRenderingBackendCallbacks->Impl_NewFrame_3D();
Impl_NewFrame_PlatformBackend();
{
// Workaround against SDL clock that sometimes leads to io.DeltaTime=0.f on emscripten
// (which fails to an `IM_ASSERT(io.DeltaTime) > 0` in ImGui::NewFrame())
//
// This can be removed once the commit 07490618 was merged into imgui docking branch
// (see https://github.com/ocornut/imgui/commit/07490618ae47fdb9f625565fbb183593170a6a72)
auto & io = ImGui::GetIO();
if (io.DeltaTime <= 0.f)
io.DeltaTime = 1.f / 60.f;
}
if (true_gil) // New Frame / Rendering and Platform Backend (not ImGui)
{ // SCOPED_RELEASE_GIL_ON_MAIN_THREAD start
SCOPED_RELEASE_GIL_ON_MAIN_THREAD;

mRenderingBackendCallbacks->Impl_NewFrame_3D();
Impl_NewFrame_PlatformBackend();
{
// Workaround against SDL clock that sometimes leads to io.DeltaTime=0.f on emscripten
// (which fails to an `IM_ASSERT(io.DeltaTime) > 0` in ImGui::NewFrame())
//
// This can be removed once the commit 07490618 was merged into imgui docking branch
// (see https://github.com/ocornut/imgui/commit/07490618ae47fdb9f625565fbb183593170a6a72)
auto &io = ImGui::GetIO();
if (io.DeltaTime <= 0.f)
io.DeltaTime = 1.f / 60.f;
}

} // SCOPED_RELEASE_GIL_ON_MAIN_THREAD end

// ImGui::NewFrame may call ImGuiTestEngine_PostNewFrame, which in turn handles the GIL in its own way,
// so that it can *NOT* be called inside SCOPED_RELEASE_GIL_ON_MAIN_THREAD
ImGui::NewFrame();


// Fight against potential font loading issue
// Fonts are transferred to the GPU one the first call to ImGui::NewFrame()
// We might detect an OpenGL error if the font texture was too big for the GPU
bool foundPotentialFontLoadingError = false;

if (true) // check potential OpenGL error on first frame, that may be due to a font loading error
{
#ifdef HELLOIMGUI_HAS_OPENGL
#ifdef HELLOIMGUI_HAS_OPENGL
if (mIdxFrame == 0)
{
auto error = glGetError();
if (error != 0)
foundPotentialFontLoadingError = true;
}
#endif
#endif
}


// CustomBackground is a user callback
if (params.callbacks.CustomBackground)
params.callbacks.CustomBackground();
else
mRenderingBackendCallbacks->Impl_Frame_3D_ClearColor(params.imGuiWindowParams.backgroundColor);

// iii/ At the end of the second frame, we measure the size of the widgets and use it as the application window size, if the user required auto size
// ==> Note: RenderGui() may measure the size of the window and resize it if mIdxFrame==1
// RenderGui may call many user callbacks, so it should not be inside SCOPED_RELEASE_GIL_ON_MAIN_THREAD
RenderGui();

if (params.callbacks.BeforeImGuiRender)
params.callbacks.BeforeImGuiRender();

ImGui::Render();
mRenderingBackendCallbacks->Impl_RenderDrawData_To_3D();
if (true_gil) // Render and Swap
{ // SCOPED_RELEASE_GIL_ON_MAIN_THREAD start
SCOPED_RELEASE_GIL_ON_MAIN_THREAD;

ImGui::Render();
mRenderingBackendCallbacks->Impl_RenderDrawData_To_3D();

if (ImGui::GetIO().ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
Impl_UpdateAndRenderAdditionalPlatformWindows();
if (ImGui::GetIO().ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
Impl_UpdateAndRenderAdditionalPlatformWindows();

Impl_SwapBuffers();
Impl_SwapBuffers();
} // SCOPED_RELEASE_GIL_ON_MAIN_THREAD end

// AfterSwap is a user callback, so it should not be inside SCOPED_RELEASE_GIL_ON_MAIN_THREAD
if (params.callbacks.AfterSwap)
params.callbacks.AfterSwap();

#ifdef HELLOIMGUI_WITH_TEST_ENGINE
#ifdef HELLOIMGUI_WITH_TEST_ENGINE
// TestEngineCallbacks::PostSwap() handles the GIL in its own way,
// it can not be called inside SCOPED_RELEASE_GIL_ON_MAIN_THREAD
if (params.useImGuiTestEngine)
{
TestEngineCallbacks::PostSwap();
#endif
}
#endif

if (foundPotentialFontLoadingError)
ReloadFontIfFailed();
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