allow for gamepad triggers to be used as buttons

Allots special buttons for use by gamepad triggers. This allows triggers to be
usable as an axis or a button depending on the control type.

NOTE: This is implemented in a way that shouldn't break compatiblity with
other builds using the same cc profile. It does not use the control config code
that appears to allow for axis buttons due to it not being fully implemented
and needing too much work for sort out. Should that ever happen this feature
should be revisited so that it can be implemented properly.

Author: notimaginative

code/controlconfig/controlsconfigcommon.cpp

@@ -2589,25 +2589,51 @@ void CC_bind::invert_toggle() {
 	flags ^= CCF_INVERTED;
 }
 
+
+static bool compare_btn(short cid, const CC_bind& A, char& A_flags, const CC_bind& B, char& B_flags)
+{
+	auto A_btn = A.get_btn();
+	auto B_btn = B.get_btn();
+
+	auto current = io::joystick::getPlayerJoystick(cid);
+
+	if (current && current->isGamepad()) {
+		if (A_btn >= SDL_GAMEPAD_BUTTON_COUNT) {
+			A_btn = (A_btn - SDL_GAMEPAD_BUTTON_COUNT) + SDL_GAMEPAD_AXIS_LEFT_TRIGGER;
+			A_flags |= CCF_AXIS_BTN;
+		}
+
+		if (B_btn >= SDL_GAMEPAD_BUTTON_COUNT) {
+			B_btn = (B_btn - SDL_GAMEPAD_BUTTON_COUNT) + SDL_GAMEPAD_AXIS_LEFT_TRIGGER;
+			B_flags |= CCF_AXIS_BTN;
+		}
+	}
+
+	return (A_btn == B_btn);
+}
+
 bool CC_bind::conflicts_with(const CC_bind& B) const {
+	char A_flags = flags;
+	char B_flags = B.flags;
+
 	// Bail early if CID or btn are not the same
-	if ((cid != B.cid) || (btn != B.btn)) {
+	if ((cid != B.cid) || !compare_btn(cid, *this, A_flags, B, B_flags)) {
 		return false;
 	}
 
 	// Check if A is an Axis or Axis Button, and if B is an Axis or Axis Button
 	char mask = (CCF_AXIS_BTN | CCF_AXIS);
-	if ((flags & mask) && (B.flags & mask)) {
+	if ((A_flags & mask) && (B_flags & mask)) {
 		return true;
 	}
 
 	// Check if Hat
-	if (flags & B.flags & CCF_HAT) {
+	if (A_flags & B_flags & CCF_HAT) {
 		return true;
 	}
 
 	// Check if Ball
-	if (flags & B.flags & CCF_BALL) {
+	if (A_flags & B_flags & CCF_BALL) {
 		return true;
 	}
 
@@ -2619,7 +2645,7 @@ bool CC_bind::conflicts_with(const CC_bind& B) const {
 	// First off, check if A or B is NOT a button, as according to the mask.  Buttons do not have a flag, so we check
 	// if they are any of the other input types
 	// Next, we return the inverse of the result. Negative of a Negative = Positive. Not Not a button = Is a button
-	return !((flags | B.flags) & mask);
+	return !((A_flags | B_flags) & mask);
 }
 
 bool CC_bind::is_inverted() const {
@@ -2710,10 +2736,19 @@ SCP_string CC_bind::textify() const {
 		case CID_JOY0:
 		case CID_JOY1:
 		case CID_JOY2:
-		case CID_JOY3:
-			Assert((btn >= 0) && (btn < JOY_TOTAL_BUTTONS));
-			retval = SCP_string(textify_button(btn));
+		case CID_JOY3: {
+			auto axis = joy_get_button_axis(cid, btn);
+
+			if (axis < 0) {
+				Assert((btn >= 0) && (btn < JOY_TOTAL_BUTTONS));
+				retval = SCP_string(textify_button(btn));
+			} else {
+				Assert((axis >= 0) && (axis < NUM_AXIS_TEXT));
+				retval = SCP_string(Axis_text[axis]);
+			}
+
 			break;
+		}
 
 		case CID_NONE:
 		default:

code/io/joy-sdl.cpp

@@ -844,7 +844,8 @@ namespace joystick
 		if (_isGamepad) {
 			// gamepads may not support all buttons, but they don't necessarily match
 			// the number or index of what's reported by the joystick api either
-			_button.resize(static_cast<size_t>(SDL_GAMEPAD_BUTTON_COUNT));
+			// NOTE: +2 added so we can map left & right triggers to a button
+			_button.resize(static_cast<size_t>(SDL_GAMEPAD_BUTTON_COUNT + 2));
 			for (size_t i = 0; i < _button.size(); ++i) {
 				if (SDL_GetGamepadButton(_gamepad, static_cast<SDL_GamepadButton>(i))) {
 					_button[i].DownTimestamp = ui_timestamp();
@@ -977,15 +978,30 @@ namespace joystick
 
 		Assertion(axis < numAxes(), "SDL event contained invalid axis index!");
 
-		// Triggers range from 0..32767 so we need to scale the value for FSO
-		// since it expects a full -32768..32767 range. Note that precision is
-		// lost in the scaling so only scale if it's not a min/max trigger value
 		if ((axis == SDL_GAMEPAD_AXIS_LEFT_TRIGGER) || (axis == SDL_GAMEPAD_AXIS_RIGHT_TRIGGER)) {
+			// Triggers range from 0..32767 so we need to scale the value for FSO
+			// since it expects a full -32768..32767 range. Note that precision is
+			// lost in the scaling so only scale if it's not a min/max trigger value
 			if (value == 0) {
 				value = -32768;
 			} else if (value < 32767) {
 				value = static_cast<decltype(value)>((value * 2) - 32768);
 			}
+
+			// We can also take this opportunity to map triggers to a button
+			int button = SDL_GAMEPAD_BUTTON_COUNT + (axis - SDL_GAMEPAD_AXIS_LEFT_TRIGGER);
+			bool down = (value >= 0);
+
+			Assertion(button < numButtons(), "Gamepad trigger button is out of bounds!");
+
+			// We also need to avoid bumping DownCount for every tiny axis movement.
+			if ( !down || (_button[button].DownCount == 0) ) {
+				_button[button].DownTimestamp = down ? ui_timestamp() : UI_TIMESTAMP::invalid();
+
+				if (down) {
+					++_button[button].DownCount;
+				}
+			}
 		}
 
 		_axisValues[axis] = value;
@@ -1434,3 +1450,26 @@ bool joy_present(short cid) {
 
 	return pJoystick[cid] != nullptr;
 }
+
+// Check for special trigger buttons and return axis for button
+// This is primarily for easier UI/UX in controlconfig (like conflict detection)
+// returns axis or -1 if not an axis button
+short joy_get_button_axis(short cid, short btn)
+{
+	auto current = io::joystick::getPlayerJoystick(cid);
+
+	// gamepads only (for now?)
+	if ( !current || !current->isGamepad() ) {
+		return -1;
+	}
+
+	// the special trigger buttons are extended on normal buttons so we need to
+	// remove those and sort out whether this is the left (0) or right (1) trigger
+	auto axis_button = btn - SDL_GAMEPAD_BUTTON_COUNT;
+
+	if (axis_button < 0 || axis_button > 1) {
+		return -1;
+	}
+
+	return static_cast<short>(SDL_GAMEPAD_AXIS_LEFT_TRIGGER + axis_button);
+}

code/io/joy.h

@@ -383,6 +383,8 @@ int joy_down_count(const CC_bind &bind, int reset_count);
 
 int joy_down(const CC_bind &bind);
 
+short joy_get_button_axis(const short cid, short btn);
+
 /**
  * Checks if the given joystick is present or not
  */