api: check for window focus when accepting input (#317)

## Link to GitHub Issue, if one exists
Fixes #139 

## Description of change
Add an option for detecting window focus when accepting input.

The new default will be to have the following:
 * naive bindings will check for window focus
* rawinput binds are not affected, will continue to be accepted
regardless of focus

Other options (always / never choices) can be picked by the user to
tweak the behavior if needed.

Clean up usage of `0xff` constant to represent invalid naive vkey.

## Testing
Still in progress, especially in regards to performance.

On a i7-9700 system, 10000 calls to `superexit::has_focus()` takes
250-350 microseconds, so this should not be a big deal at all.

src/spice2x/cfg/api.cpp

@@ -1,5 +1,8 @@
 #include "api.h"
 
+#include <optional>
+
+#include "launcher/superexit.h"
 #include "rawinput/rawinput.h"
 #include "rawinput/piuio.h"
 #include "util/time.h"
@@ -64,18 +67,29 @@ GameAPI::Buttons::State GameAPI::Buttons::getState(rawinput::RawInputManager *ma
     auto current_button = &_button;
     auto alternatives = check_alts ? &current_button->getAlternatives() : nullptr;
     unsigned int button_count = 0;
+    std::optional<bool> window_has_focus;
     while (true) {
 
         // naive behavior
         if (current_button->isNaive()) {
+            GameAPI::Buttons::State state;
+            auto vkey = current_button->getVKey();
+
+            // check for focus
+            if (vkey != INVALID_VKEY && rawinput::NAIVE_REQUIRE_FOCUS) {
+                if (!window_has_focus.has_value()) {
+                    window_has_focus = superexit::has_focus();
+                }
+                if (!window_has_focus.value()) {
+                    vkey = INVALID_VKEY;
+                }
+            }
 
             // read
-            auto vkey = current_button->getVKey();
-            GameAPI::Buttons::State state;
-            if (vkey == 0xFF) {
+            if (vkey == INVALID_VKEY) {
                 state = BUTTON_NOT_PRESSED;
             } else {
-                state = (GetAsyncKeyState(current_button->getVKey()) & 0x8000) ? BUTTON_PRESSED : BUTTON_NOT_PRESSED;
+                state = (GetAsyncKeyState(vkey) & 0x8000) ? BUTTON_PRESSED : BUTTON_NOT_PRESSED;
             }
 
             // invert
@@ -106,6 +120,16 @@ GameAPI::Buttons::State GameAPI::Buttons::getState(rawinput::RawInputManager *ma
         auto &devid = current_button->getDeviceIdentifier();
         auto device = manager->devices_get(devid, false); // TODO: fix to update only
 
+        // check for focus
+        if (device && rawinput::RAWINPUT_REQUIRE_FOCUS) {
+            if (!window_has_focus.has_value()) {
+                window_has_focus = superexit::has_focus();
+            }
+            if (!window_has_focus.value()) {
+                device = nullptr;
+            }
+        }
+
         // get state if device was marked as updated
         GameAPI::Buttons::State state = current_button->getLastState();
         double *last_up = nullptr;
@@ -571,6 +595,12 @@ float GameAPI::Analogs::getState(rawinput::Device *device, Analog &analog) {
     switch (device->type) {
         case rawinput::MOUSE: {
 
+            // check for focus
+            if (rawinput::NAIVE_REQUIRE_FOCUS && !superexit::has_focus()) {
+                value = analog.getLastState();
+                break;
+            }
+
             // get mouse position
             auto mouse = device->mouseInfo;
             long pos;

src/spice2x/cfg/button.cpp

@@ -284,7 +284,7 @@ std::string Button::getDisplayString(rawinput::RawInputManager* manager) {
     std::string vKeyString = fmt::format("{:#x}", vKey);
 
     // device must be existing
-    if (this->device_identifier.empty() && vKey == 0xFF) {
+    if (this->device_identifier.empty() && vKey == INVALID_VKEY) {
         return "";
     }
 

src/spice2x/cfg/button.h

@@ -33,12 +33,14 @@ enum ButtonAnalogType {
 
 extern const char *ButtonAnalogTypeStr[];
 
+constexpr unsigned short INVALID_VKEY = UINT16_C(0xFF);
+
 class Button {
 private:
     std::vector<Button> alternatives;
     std::string name;
     std::string device_identifier = "";
-    unsigned short vKey = 0xFF;
+    unsigned short vKey = INVALID_VKEY;
     ButtonAnalogType analog_type = BAT_NONE;
     double debounce_up = 0.0;
     double debounce_down = 0.0;
@@ -68,12 +70,12 @@ public:
         if (this->override_enabled) {
             return true;
         }
-        if (this->vKey != 0xFF) {
+        if (this->vKey != INVALID_VKEY) {
             return true;
         }
 
         for (auto &alternative : this->alternatives) {
-            if (alternative.vKey != 0xFF) {
+            if (alternative.vKey != INVALID_VKEY) {
                 return true;
             }
         }
@@ -82,7 +84,7 @@ public:
     }
 
     inline void clearBindings() {
-        vKey = 0xFF;
+        vKey = INVALID_VKEY;
         alternatives.clear();
         device_identifier = "";
         analog_type = BAT_NONE;