Support mouse relative mode via submission queue

This commit adds support for automatic mouse capture control via the new
submission queue feature. With this modification, the cursor will be
captured once the game screen become visible and be released when the
menu is opened.

Author: alanjian85

src/i_system.h

@@ -89,6 +89,7 @@ void I_Tactile (int on, int off, int total);
 
 void I_Error (char *error, ...);
 
+void I_SetRelativeMode(boolean enabled);
 
 #endif
 //-----------------------------------------------------------------------------

src/m_menu.c

@@ -1700,6 +1700,7 @@ void M_StartControlPanel (void)
         return;
 
     menuactive = 1;
+    I_SetRelativeMode(false);
     currentMenu = &MainDef;         // JDC
     itemOn = currentMenu->lastOn;   // JDC
 }
@@ -1784,6 +1785,7 @@ void M_Drawer (void)
 void M_ClearMenus (void)
 {
     menuactive = 0;
+    I_SetRelativeMode(true);
     // if (!netgame && usergame && paused)
     //       sendpause = true;
 }

src/riscv/i_system.c

@@ -108,17 +108,31 @@ static submission_queue_t submission_queue = {
 static unsigned int event_count = 0;
 const int queues_capacity = 128;
 
+void
+I_SetRelativeMode(boolean enabled)
+{
+	emu_submission_t submission;
+	submission.type = RELATIVE_MODE_SUBMISSION;
+	submission.mouse.enabled = enabled;
+	submission_queue.base[submission_queue.end++] = submission;
+	submission_queue.end &= queues_capacity - 1;
+	register int a0 asm("a0") = 1;
+	register int a7 asm("a7") = 0xfeed;
+	asm volatile("scall" : "+r"(a0) : "r"(a7));
+}
+
 void
 I_Init(void)
 {
 	void *base = malloc(sizeof(emu_event_t) * queues_capacity + sizeof(emu_submission_t) * queues_capacity);
 	event_queue.base = base;
-	submission_queue.base = base;
+	submission_queue.base = base + sizeof(emu_event_t) * queues_capacity;
 	register int a0 asm("a0") = (uintptr_t) base;
 	register int a1 asm("a1") = queues_capacity;
 	register int a2 asm("a2") = (uintptr_t) &event_count;
 	register int a7 asm("a7") = 0xc0de;
 	asm volatile("scall" : "+r"(a0) : "r"(a1), "r"(a2), "r"(a7));
+	I_SetRelativeMode(true);
 }