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ImGui: Add support for ImGuiBackendFlags_HasSetMousePos and cleaner drawFrame() code #102

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ImGui: Add support for ImGuiBackendFlags_HasSetMousePos and cleaner drawFrame() code #102

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211c492
ImGui: Use framebuffer info from ImDrawData instead of InGui::IO()
Auburn Apr 23, 2023
83a240d
ImGui: Support io.WantSetMousePos (ImGuiBackendFlags_HasSetMousePos)
Auburn Apr 23, 2023
803c9d2
Use SFINAE to only call warpCursor if the Application supports it
Auburn Apr 23, 2023
982a9db
Add tests for ImGui io.WantSetMousePos
Auburn Apr 24, 2023
998fcd3
Add templated constructors for ImGui Context
Auburn Apr 26, 2023
57bd3e2
ImGui tests: fix naming, improve tests
Auburn Apr 26, 2023
36f0845
Fix bad attempt to be clever
Auburn Apr 26, 2023
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14 changes: 8 additions & 6 deletions src/Magnum/ImGuiIntegration/Context.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -85,6 +85,8 @@ Context::Context(ImGuiContext& context, const Vector2& size, const Vector2i& win

/* Tell ImGui that changing mouse cursors is supported */
io.BackendFlags |= ImGuiBackendFlags_HasMouseCursors;
/* We can honor io.WantSetMousePos requests */
io.BackendFlags |= ImGuiBackendFlags_HasSetMousePos;

/* Check if we can support base vertex > 0 in draw commands */
#if !(defined(MAGNUM_TARGET_WEBGL) && defined(MAGNUM_TARGET_GLES2))
Expand Down Expand Up @@ -312,17 +314,17 @@ void Context::drawFrame() {

ImGui::Render();

ImGuiIO& io = ImGui::GetIO();
const Vector2 fbSize = Vector2{io.DisplaySize}*Vector2{io.DisplayFramebufferScale};
if(!fbSize.product()) return;

ImDrawData* drawData = ImGui::GetDrawData();
CORRADE_INTERNAL_ASSERT(drawData); /* This is always valid after Render() */
drawData->ScaleClipRects(io.DisplayFramebufferScale);

const Vector2 fbSize = Vector2{drawData->DisplaySize}*Vector2{drawData->FramebufferScale};
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Hm, I can't tell if this is a good or a bad change as my knowledge of ImGui is rather bad 😅 How does drawData->FramebufferScale and io.DisplayFramebufferScale relate?

Cc: @pezcode, you're responsible for most of the code here I think, and I bet you know better than me :)

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From the ImGui comments:

ImVec2          DisplayPos;             // Top-left position of the viewport to render (== top-left of the orthogonal projection matrix to use) (== GetMainViewport()->Pos for the main viewport, == (0.0) in most single-viewport applications)
ImVec2          DisplaySize;            // Size of the viewport to render (== GetMainViewport()->Size for the main viewport, == io.DisplaySize in most single-viewport applications)
ImVec2          FramebufferScale;       // Amount of pixels for each unit of DisplaySize. Based on io.DisplayFramebufferScale. Generally (1,1) on normal display, (2,2) on OSX with Retina display.

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It's mainly to aid with multi-window rendering 😉

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I see, that makes sense then :)

if(!fbSize.product()) return;

drawData->ScaleClipRects(drawData->FramebufferScale);

const Matrix3 projection =
Matrix3::translation({-1.0f, 1.0f})*
Matrix3::scaling({2.0f/Vector2(io.DisplaySize)})*
Matrix3::scaling({2.0f/Vector2(drawData->DisplaySize)})*
Matrix3::scaling({1.0f, -1.0f});
_shader.setTransformationProjectionMatrix(projection);

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12 changes: 12 additions & 0 deletions src/Magnum/ImGuiIntegration/Context.hpp
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Expand Up @@ -337,12 +337,24 @@ MAGNUM_IMGUIINTEGRATION_OPTIONAL_CURSOR(No)
#undef MAGNUM_IMGUIINTEGRATION_OPTIONAL_CURSOR
#endif

template<class... T> void callWarpCursor(const T&...) {}

template<class Application, class = decltype(&Application::warpCursor)>
void callWarpCursor(Application& application, const Vector2i& position) {
application.warpCursor(position);
}
}

template<class Application> void Context::updateApplicationCursor(Application& application) {
/* Ensure we use the context we're linked to */
ImGui::SetCurrentContext(_context);

ImGuiIO& io = ImGui::GetIO();

if(io.WantSetMousePos) {
Implementation::callWarpCursor(application, Vector2i(Vector2(io.MousePos)/_eventScaling));
}

switch(ImGui::GetMouseCursor()) {
case ImGuiMouseCursor_TextInput:
application.setCursor(Application::Cursor::TextInput);
Expand Down
39 changes: 31 additions & 8 deletions src/Magnum/ImGuiIntegration/Test/ContextGLTest.cpp
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Expand Up @@ -114,8 +114,11 @@ struct Application {
None = 999
};

void setCursor(Cursor cursor) { currentCursor = cursor; }
Cursor currentCursor = Cursor::None;
Cursor _currentCursor = Cursor::None;
Vector2i _mousePos;
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void setCursor(Cursor cursor) { _currentCursor = cursor; }
void warpCursor(const Vector2i& pos) { _mousePos = pos; }
};

struct KeyEvent: public InputEvent {
Expand Down Expand Up @@ -752,34 +755,54 @@ void ContextGLTest::textInput() {
}

void ContextGLTest::updateCursor() {
Context c{{}};
Context c{{200, 200}, {400, 400}, {300, 300}};

Application app;

/* Default (should be an arrow) */
c.updateApplicationCursor(app);
CORRADE_VERIFY(app.currentCursor == Application::Cursor::Arrow);
CORRADE_VERIFY(app._currentCursor == Application::Cursor::Arrow);

/* Change to a cursor that is present in all apps */
ImGui::SetMouseCursor(ImGuiMouseCursor_Hand);
c.updateApplicationCursor(app);
CORRADE_VERIFY(app.currentCursor == Application::Cursor::Hand);
CORRADE_VERIFY(app._currentCursor == Application::Cursor::Hand);

/* Change to a cursor that is unknown -> fallback to an arrow */
ImGui::SetMouseCursor(ImGuiMouseCursor_COUNT);
c.updateApplicationCursor(app);
CORRADE_VERIFY(app.currentCursor == Application::Cursor::Arrow);
CORRADE_VERIFY(app._currentCursor == Application::Cursor::Arrow);

/* Change to a cursor that is conditional but present in this app */
ImGui::SetMouseCursor(ImGuiMouseCursor_ResizeAll);
c.updateApplicationCursor(app);
CORRADE_VERIFY(app.currentCursor == Application::Cursor::ResizeAll);
CORRADE_VERIFY(app._currentCursor == Application::Cursor::ResizeAll);

/* Change to a cursor that is conditional and not present -> fallback to
an arrow */
ImGui::SetMouseCursor(ImGuiMouseCursor_ResizeNESW);
c.updateApplicationCursor(app);
CORRADE_VERIFY(app.currentCursor == Application::Cursor::Arrow);
CORRADE_VERIFY(app._currentCursor == Application::Cursor::Arrow);

/* Change to imgui mouse pos and mark it as changed
Account for 2x DPI scaling in equality check */
ImGuiIO& io = ImGui::GetIO();
io.MousePos = ImVec2(10, 10);
io.WantSetMousePos = true;
c.updateApplicationCursor(app);
CORRADE_VERIFY(app._mousePos == Vector2i(20, 20));

/* Change to imgui mouse pos without marking it as changed */
io.MousePos = ImVec2(50, 50);
io.WantSetMousePos = false;
c.updateApplicationCursor(app);
CORRADE_VERIFY(app._mousePos == Vector2i(20, 20));

/* Mark mouse pos changed */
io.WantSetMousePos = true;
c.updateApplicationCursor(app);
CORRADE_VERIFY(app._mousePos == Vector2i(100, 100));

}

void ContextGLTest::multipleContexts() {
Expand Down