overlay: mouse-as-touch needs to check if subscreen window is active (#842)

## Link to GitHub Issue or related Pull Request, if one exists
Fixes #840 

## Description of change
Currently, for subscreen games, mouse events are still delivered even
when the subscreen overlay window is not visible.

Change this so that the subscreen overlay must be active and under the
mouse cursor for the mouse-to-touch transformation to occur. Applies to
both native and wintouchemu.

## Testing
Needs to test everything again..

iidx:

- [ ]  full screen with overlay
- [ ]  single window with overlay
- [ ]  two window

Test: mouse, poke, api, real touch screen

sdvx:

- [ ] full screen with overlay
- [ ] windowed

popn

- [x] full screen with overlay
- [x] window with overlay
- [x] dedicated window

gitadora

- [x] single window with overlay
- [x] dedicated sub window

nostalgia

- [x] fullscreen
- [x] windowed

test: poke

wintouchemu
- [ ] Do all of the above again with wintouchemu

src/spice2x/overlay/overlay.cpp

@@ -908,6 +908,17 @@ bool overlay::SpiceOverlay::get_active() {
     return this->active;
 }
 
+bool overlay::SpiceOverlay::is_subscreen_overlay_visible() {
+    return this->get_active() &&
+        this->window_sub != nullptr &&
+        this->window_sub->get_active();
+}
+
+bool overlay::SpiceOverlay::accepts_subscreen_mouse_input() {
+    return this->is_subscreen_overlay_visible() &&
+        this->window_sub->is_mouse_hovered();
+}
+
 bool overlay::SpiceOverlay::has_focus() {
     return this->get_active() && ImGui::IsWindowFocused(ImGuiFocusedFlags_AnyWindow);
 }

src/spice2x/overlay/overlay.h

@@ -109,6 +109,7 @@ namespace overlay {
         void show_main_menu();
         void set_active(bool active);
         bool get_active();
+        bool accepts_subscreen_mouse_input();
         bool has_focus();
         bool hotkeys_triggered();
 
@@ -143,20 +144,20 @@ namespace overlay {
             return this->hWnd;
         }
 
-        bool can_transform_touch_input() {
-            return (this->subscreen_mouse_handler != nullptr);
+        bool has_subscreen_touch_transform() {
+            return (this->subscreen_touch_transform != nullptr);
         }
 
         bool transform_touch_point(LONG *x, LONG *y) {
-            if (this->get_active() && this->subscreen_mouse_handler) {
-                return this->subscreen_mouse_handler(x, y);
+            if (this->get_active() && this->subscreen_touch_transform) {
+                return this->subscreen_touch_transform(x, y);
             } else {
                 return true;
             }
         }
 
-        void set_subscreen_mouse_handler(const std::function<bool(LONG *, LONG *)> &f) {
-            this->subscreen_mouse_handler = f;
+        void set_subscreen_touch_transform(const std::function<bool(LONG *, LONG *)> &f) {
+            this->subscreen_touch_transform = f;
         }
 
         // renderer
@@ -203,7 +204,7 @@ namespace overlay {
 
         std::vector<std::unique_ptr<Window>> windows;
 
-        std::function<bool(LONG *, LONG *)> subscreen_mouse_handler = nullptr;
+        std::function<bool(LONG *, LONG *)> subscreen_touch_transform = nullptr;
 
         bool active = false;
         bool toggle_down = false;
@@ -216,6 +217,7 @@ namespace overlay {
         // so render() never runs without a matching NewFrame.
         bool has_pending_frame = false;
 
+        bool is_subscreen_overlay_visible();
         void init();
         void add_font(const char* font, ImFontConfig* config, const ImWchar* glyphs);
     };

src/spice2x/overlay/window.cpp

@@ -69,6 +69,7 @@ void overlay::Window::build() {
 
     // check if active
     if (!this->active) {
+        this->mouse_hovered = false;
         return;
     }
 
@@ -106,10 +107,18 @@ void overlay::Window::build() {
         // top spot. suppress that so only an explicit focus request (see below)
         // decides what comes to the front.
         const std::string window_id = this->title + "###" + to_string(this);
-        if (ImGui::Begin(
+        const bool build_contents = ImGui::Begin(
                 window_id.c_str(),
                 &this->active,
-                this->flags | ImGuiWindowFlags_NoFocusOnAppearing)) {
+                this->flags | ImGuiWindowFlags_NoFocusOnAppearing);
+
+        // keep the window hovered while its invisible input button is held during a drag
+        this->mouse_hovered =
+            ImGui::IsWindowHovered(
+                ImGuiHoveredFlags_RootAndChildWindows |
+                ImGuiHoveredFlags_AllowWhenBlockedByActiveItem);
+
+        if (build_contents) {
 
             // window attributes - init_pos / init_size are only honored once
             // (ImGuiCond_Once), so compute them a single time instead of every frame
@@ -154,6 +163,9 @@ void overlay::Window::build() {
 
     } else {
 
+        // raw content does not have an ImGui window to hover
+        this->mouse_hovered = false;
+
         // add raw content
         this->build_content();
     }
@@ -201,3 +213,7 @@ bool overlay::Window::get_active() {
     // now it depends on us
     return this->active;
 }
+
+bool overlay::Window::is_mouse_hovered() {
+    return this->mouse_hovered;
+}

src/spice2x/overlay/window.h

@@ -24,6 +24,7 @@ namespace overlay {
         void toggle_active();
         void set_active(bool active);
         bool get_active();
+        bool is_mouse_hovered();
 
         // raise this window to the top of the z-order on its next build. only
         // call in response to an explicit user action (keyboard toggle, UI
@@ -37,6 +38,7 @@ namespace overlay {
         // set when the window transitions to visible so build() raises it to the
         // top of the z-order on the next frame
         bool request_focus = false;
+        bool mouse_hovered = false;
         std::vector<Window*> children;
 
         // settings

src/spice2x/overlay/windows/generic_sub.cpp

@@ -42,7 +42,7 @@ namespace overlay::windows {
         this->texture_width = 0;
         this->texture_height = 0;
 
-        overlay->set_subscreen_mouse_handler([this](LONG *x, LONG *y) -> bool {
+        overlay->set_subscreen_touch_transform([this](LONG *x, LONG *y) -> bool {
             // convert to normalized form (relative window coordinates 0.f-1.f)
             ImVec2 xy;