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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: 7 additions & 7 deletions src/Magnum/ImGuiIntegration/Context.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -85,7 +85,7 @@ Context::Context(ImGuiContext& context, const Vector2& size, const Vector2i& win

/* Tell ImGui that changing mouse cursors is supported */
io.BackendFlags |= ImGuiBackendFlags_HasMouseCursors;

/* Check if we can support base vertex > 0 in draw commands */
#if !(defined(MAGNUM_TARGET_WEBGL) && defined(MAGNUM_TARGET_GLES2))
if(
Expand Down Expand Up @@ -312,17 +312,17 @@ 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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14 changes: 14 additions & 0 deletions src/Magnum/ImGuiIntegration/Context.h
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Expand Up @@ -378,6 +378,20 @@ class MAGNUM_IMGUIINTEGRATION_EXPORT Context {
*/
explicit Context(ImGuiContext& context, const Vector2i& size);

/**
* @brief TODO
*
* Implicitly fetches framebuffer and window size from the application instance
* Using this template constructor is preferable as it enables additional features based on given Application capabilities
*/
template<class Application> explicit Context(const Vector2& size, const Application& application);

/**
* @brief TODO
*
*/
template<class Application> explicit Context(ImGuiContext& context, const Vector2& size, const Application& application);

/**
* @brief Construct without creating the underlying ImGui context
*
Expand Down
26 changes: 26 additions & 0 deletions src/Magnum/ImGuiIntegration/Context.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,20 @@
#include "Magnum/ImGuiIntegration/Context.h"

namespace Magnum { namespace ImGuiIntegration {
namespace Implementation {
template<class Application, class = decltype(&Application::warpCursor)>
constexpr static bool hasWarpCursor(const Application&) { return true; }

template<class... T> constexpr static bool hasWarpCursor(const T&...) { return false; }
}

template<class Application> Context::Context(const Vector2& size, const Application& application): Context{*ImGui::CreateContext(), size, application} {}

template<class Application> Context::Context(ImGuiContext& context, const Vector2& size, const Application& application): Context{context, size, application.windowSize(), application.framebufferSize()} {
/* We can honor io.WantSetMousePos requests if application type supports it */
if(Implementation::hasWarpCursor(application))
ImGui::GetIO().BackendFlags |= ImGuiBackendFlags_HasSetMousePos;
}

template<class KeyEvent> bool Context::handleKeyEvent(KeyEvent& event, bool value) {
/* Ensure we use the context we're linked to */
Expand Down Expand Up @@ -337,12 +351,24 @@ MAGNUM_IMGUIINTEGRATION_OPTIONAL_CURSOR(No)
#undef MAGNUM_IMGUIINTEGRATION_OPTIONAL_CURSOR
#endif

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

template<class Application, class = decltype(&Application::warpCursor)>
static 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
27 changes: 25 additions & 2 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;
Vector2i mousePos;

void setCursor(Cursor cursor) { currentCursor = cursor; }
void warpCursor(const Vector2i& pos) { mousePos = pos; }
};

struct KeyEvent: public InputEvent {
Expand Down Expand Up @@ -752,7 +755,7 @@ void ContextGLTest::textInput() {
}

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

Application app;

Expand Down Expand Up @@ -780,6 +783,26 @@ void ContextGLTest::updateCursor() {
ImGui::SetMouseCursor(ImGuiMouseCursor_ResizeNESW);
c.updateApplicationCursor(app);
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, 15);
io.WantSetMousePos = true;
c.updateApplicationCursor(app);
CORRADE_VERIFY(app.mousePos == Vector2i(20, 30));

/* Change to imgui mouse pos without marking it as changed */
io.MousePos = ImVec2(50, 0);
io.WantSetMousePos = false;
c.updateApplicationCursor(app);
CORRADE_VERIFY(app.mousePos == Vector2i(20, 30));

/* Mark mouse pos changed */
io.WantSetMousePos = true;
c.updateApplicationCursor(app);
CORRADE_VERIFY(app.mousePos == Vector2i(100, 0));

}

void ContextGLTest::multipleContexts() {
Expand Down