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store persistent state in backend data as per imgui norms

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This commit is contained in:
SlowRiot 2026-03-31 16:08:35 +01:00
parent ff4341d3d6
commit 6d6d7d5f0f
1 changed files with 45 additions and 20 deletions
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65
backends/imgui_impl_emscripten.cpp
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@ -317,6 +317,23 @@ void set(std::string const& new_cursor)
namespace {
struct ImGui_ImplEmscripten_Data
{
emscripten_browser_cursor_internal::cursor CurrentCursor;
std::optional<std::string> CursorToRestore;
ImGui_ImplEmscripten_Data()
: CurrentCursor{emscripten_browser_cursor_internal::cursor::invalid}
{
}
};
// Backend data stored in io.BackendPlatformUserData to allow support for multiple Dear ImGui contexts
ImGui_ImplEmscripten_Data* ImGui_ImplEmscripten_GetBackendData()
{
return ImGui::GetCurrentContext() ? static_cast<ImGui_ImplEmscripten_Data*>(ImGui::GetIO().BackendPlatformUserData) : nullptr;
}
void set_cursor_if_necessary(emscripten_browser_cursor_internal::cursor& current_cursor, emscripten_browser_cursor_internal::cursor new_cursor)
{
if (new_cursor == current_cursor) return; // don't do anything if the current cursor is already set
@ -324,57 +341,54 @@ void set_cursor_if_necessary(emscripten_browser_cursor_internal::cursor& current
emscripten_browser_cursor_internal::set(new_cursor);
}
void update_cursor()
void update_cursor(ImGui_ImplEmscripten_Data* bd)
{
// Sync any cursor changes due to ImGui to the browser's cursor
static emscripten_browser_cursor_internal::cursor current_cursor{emscripten_browser_cursor_internal::cursor::invalid};
static std::optional<std::string> cursor_to_restore;
if (ImGui::GetIO().WantCaptureMouse) // mouse is hovering over the gui
{
if (!cursor_to_restore && emscripten_browser_cursor_internal::is_set())
if (!bd->CursorToRestore && emscripten_browser_cursor_internal::is_set())
{
cursor_to_restore = emscripten_browser_cursor_internal::get_string(); // back up the existing cursor when entering the imgui capture space
bd->CursorToRestore = emscripten_browser_cursor_internal::get_string(); // back up the existing cursor when entering the imgui capture space
}
switch (ImGui::GetMouseCursor())
{
case ImGuiMouseCursor_Arrow:
set_cursor_if_necessary(current_cursor, emscripten_browser_cursor_internal::cursor::cursor_default);
set_cursor_if_necessary(bd->CurrentCursor, emscripten_browser_cursor_internal::cursor::cursor_default);
break;
case ImGuiMouseCursor_TextInput: // When hovering over InputText, etc.
set_cursor_if_necessary(current_cursor, emscripten_browser_cursor_internal::cursor::text);
set_cursor_if_necessary(bd->CurrentCursor, emscripten_browser_cursor_internal::cursor::text);
break;
case ImGuiMouseCursor_ResizeAll: // (Unused by Dear ImGui functions)
set_cursor_if_necessary(current_cursor, emscripten_browser_cursor_internal::cursor::move);
set_cursor_if_necessary(bd->CurrentCursor, emscripten_browser_cursor_internal::cursor::move);
break;
case ImGuiMouseCursor_ResizeNS: // When hovering over a horizontal border
set_cursor_if_necessary(current_cursor, emscripten_browser_cursor_internal::cursor::ns_resize);
set_cursor_if_necessary(bd->CurrentCursor, emscripten_browser_cursor_internal::cursor::ns_resize);
break;
case ImGuiMouseCursor_ResizeEW: // When hovering over a vertical border or a column
set_cursor_if_necessary(current_cursor, emscripten_browser_cursor_internal::cursor::ew_resize);
set_cursor_if_necessary(bd->CurrentCursor, emscripten_browser_cursor_internal::cursor::ew_resize);
break;
case ImGuiMouseCursor_ResizeNESW: // When hovering over the bottom-left corner of a window
set_cursor_if_necessary(current_cursor, emscripten_browser_cursor_internal::cursor::nesw_resize);
set_cursor_if_necessary(bd->CurrentCursor, emscripten_browser_cursor_internal::cursor::nesw_resize);
break;
case ImGuiMouseCursor_ResizeNWSE: // When hovering over the bottom-right corner of a window
set_cursor_if_necessary(current_cursor, emscripten_browser_cursor_internal::cursor::nwse_resize);
set_cursor_if_necessary(bd->CurrentCursor, emscripten_browser_cursor_internal::cursor::nwse_resize);
break;
case ImGuiMouseCursor_Hand: // (Unused by Dear ImGui functions. Use for e.g. hyperlinks)
set_cursor_if_necessary(current_cursor, emscripten_browser_cursor_internal::cursor::pointer);
set_cursor_if_necessary(bd->CurrentCursor, emscripten_browser_cursor_internal::cursor::pointer);
break;
case ImGuiMouseCursor_NotAllowed: // When hovering something with disallowed interaction. Usually a crossed circle.
set_cursor_if_necessary(current_cursor, emscripten_browser_cursor_internal::cursor::not_allowed);
set_cursor_if_necessary(bd->CurrentCursor, emscripten_browser_cursor_internal::cursor::not_allowed);
break;
}
}
else // mouse is away from the gui, hovering over some other part of the viewport
{
if (cursor_to_restore)
if (bd->CursorToRestore)
{
emscripten_browser_cursor_internal::set(*cursor_to_restore); // restore the previous cursor when leaving the imgui capture space
cursor_to_restore = std::nullopt;
current_cursor = emscripten_browser_cursor_internal::cursor::invalid; // select an unused value for current cursor to force a set next time set_cursor_if_necessary is called
emscripten_browser_cursor_internal::set(*bd->CursorToRestore); // restore the previous cursor when leaving the imgui capture space
bd->CursorToRestore = std::nullopt;
bd->CurrentCursor = emscripten_browser_cursor_internal::cursor::invalid; // select an unused value for current cursor to force a set next time set_cursor_if_necessary is called
}
}
}
@ -385,6 +399,10 @@ void ImGui_ImplEmscripten_Init()
{
// Initialise the Emscripten backend, setting input callbacks
ImGuiIO& io{ImGui::GetIO()};
IMGUI_CHECKVERSION();
IM_ASSERT(io.BackendPlatformUserData == nullptr && "Already initialized a platform backend!");
ImGui_ImplEmscripten_Data* bd{IM_NEW(ImGui_ImplEmscripten_Data)()};
io.BackendPlatformUserData = static_cast<void*>(bd);
io.BackendPlatformName = "imgui_impl_emscripten";
io.BackendFlags |= ImGuiBackendFlags_HasMouseCursors;
@ -612,6 +630,9 @@ void ImGui_ImplEmscripten_Init()
void ImGui_ImplEmscripten_Shutdown()
{
ImGui_ImplEmscripten_Data* bd{ImGui_ImplEmscripten_GetBackendData()};
IM_ASSERT(bd != nullptr && "No platform backend to shutdown, or already shutdown?");
// Unset any callbacks set by Init
emscripten_set_mousemove_callback( EMSCRIPTEN_EVENT_TARGET_WINDOW, nullptr, false, nullptr);
emscripten_set_mousedown_callback( EMSCRIPTEN_EVENT_TARGET_WINDOW, nullptr, false, nullptr);
@ -631,12 +652,16 @@ void ImGui_ImplEmscripten_Shutdown()
io.BackendPlatformName = nullptr;
io.BackendPlatformUserData = nullptr;
io.BackendFlags &= ~ImGuiBackendFlags_HasMouseCursors;
IM_DELETE(bd);
}
void ImGui_ImplEmscripten_NewFrame()
{
ImGui_ImplEmscripten_Data* bd{ImGui_ImplEmscripten_GetBackendData()};
IM_ASSERT(bd != nullptr && "Context or backend not initialized? Did you call ImGui_ImplEmscripten_Init()?");
// Update any state that needs to be polled
update_cursor();
update_cursor(bd);
}
#endif // IMGUI_DISABLE