fox32rom: Use a FIFO queue for events instead of a LIFO stack

Using a LIFO stack for events was a dumb idea in the first place, this
should've been a FIFO queue from the beginning.

This allows the system to respond to events in the same order that they
are generated, instead of always responding to the newest event first.

event.asm

@@ -1,7 +1,11 @@
 ; event system routines
 
-const event_stack:         0x01FFFFFC ; pre-decremented
+const event_queue_top:    0x01FFFFFE
-const event_stack_pointer: 0x01FFFFFC
+const event_queue_bottom: 0x01FFFBFE ; top - 0x400 (32 events * (4 bytes * (1 type + 7 parameters)))
+const event_queue_index:  0x01FFFFFF ; byte
+const event_queue_size:   32         ; 32 events
+const event_size_bytes:   32         ; 32 bytes per event
+const event_size_words:   8          ; 8 words per event
 
 ; event types
 const mouse_click_event_type:    0x00000000
@@ -15,112 +19,164 @@ const empty_event_type:          0xFFFFFFFF
 ; none
 ; outputs:
 ; r0: event type
-; r1-r5: event parameters
+; r1-r7: event parameters
 wait_for_event:
     ise
     halt
 
-    ; check the event stack pointer
+    ; if the event queue index doesn't equal zero, then at least one event is available
-    ; if equal to its base address, then the event stack is empty
+    cmp.8 [event_queue_index], 0
-    cmp [event_stack_pointer], event_stack_pointer
     ifz jmp wait_for_event
 
-    ; an event is available in the event stack, pop it from the stack and return it
+    ; an event is available in the event queue, remove it from the queue and return it
-    call pop_event
+    call get_next_event
 
     ret
 
-; push an event to the event stack
+; add an event to the event queue
 ; inputs:
 ; r0: event type
-; r1-r5: event parameters
+; r1-r7: event parameters
 ; outputs:
 ; none
-push_event:
+new_event:
-    push r6
+    ; ensure there is enough space left for another event
+    cmp.8 [event_queue_index], event_queue_size
+    ifz ret
 
-    mov r6, [event_stack_pointer]
+    push r8
-    ; TODO: check to make sure we don't accidentally clobber the system stack by pushing too many events
+    push r9
 
-    ; push r0
+    ; point to the current event queue index
-    sub r6, 4
+    mov r8, event_queue_bottom
-    mov [r6], r0
+    movz.8 r9, [event_queue_index]
+    mul r9, event_size_bytes
+    add r8, r9
 
-    ; push r1
+    ; copy the event type
-    sub r6, 4
+    mov [r8], r0
-    mov [r6], r1
+    add r8, 4
 
-    ; push r2
+    ; copy the event parameters
-    sub r6, 4
+    mov [r8], r1
-    mov [r6], r2
+    add r8, 4
+    mov [r8], r2
+    add r8, 4
+    mov [r8], r3
+    add r8, 4
+    mov [r8], r4
+    add r8, 4
+    mov [r8], r5
+    add r8, 4
+    mov [r8], r6
+    add r8, 4
+    mov [r8], r7
+    add r8, 4
 
-    ; push r3
+    ; increment the index
-    sub r6, 4
+    inc.8 [event_queue_index]
-    mov [r6], r3
 
-    ; push r4
+    pop r9
-    sub r6, 4
+    pop r8
-    mov [r6], r4
-
-    ; push r5
-    sub r6, 4
-    mov [r6], r5
-
-    mov [event_stack_pointer], r6
-
-    pop r6
     ret
 
-; pop an event from the event stack
+; get the next event and remove it from the event queue
 ; inputs:
 ; none
 ; outputs:
 ; r0: event type
-; r1-r5: event parameters
+; r1-r7: event parameters
-pop_event:
+get_next_event:
-    ; check the event stack pointer
+    ; if the event queue index equals zero, then the queue is empty
-    ; if equal to its base address, then the event stack is empty
+    cmp.8 [event_queue_index], 0
-    cmp [event_stack_pointer], event_stack_pointer
+    ifz jmp get_next_event_empty
-    ifz jmp pop_event_empty
 
-    push r6
+    icl
+    push r8
 
-    mov r6, [event_stack_pointer]
+    ; point to the bottom of the event queue
+    mov r8, event_queue_bottom
 
-    ; pop r5
+    ; copy the event type
-    mov r5, [r6]
+    mov r0, [r8]
-    add r6, 4
+    add r8, 4
 
-    ; pop r4
+    ; copy the event parameters
-    mov r4, [r6]
+    mov r1, [r8]
-    add r6, 4
+    add r8, 4
+    mov r2, [r8]
+    add r8, 4
+    mov r3, [r8]
+    add r8, 4
+    mov r4, [r8]
+    add r8, 4
+    mov r5, [r8]
+    add r8, 4
+    mov r6, [r8]
+    add r8, 4
+    mov r7, [r8]
 
-    ; pop r3
+    ; shift all events down by one
-    mov r3, [r6]
+    call shift_events
-    add r6, 4
 
-    ; pop r2
+    ; decrement the index
-    mov r2, [r6]
+    dec.8 [event_queue_index]
-    add r6, 4
 
-    ; pop r1
+    pop r8
-    mov r1, [r6]
+    ise
-    add r6, 4
-
-    ; pop r0
-    mov r0, [r6]
-    add r6, 4
-
-    mov [event_stack_pointer], r6
-
-    pop r6
     ret
-pop_event_empty:
+get_next_event_empty:
     mov r0, empty_event_type
     mov r1, 0
     mov r2, 0
     mov r3, 0
     mov r4, 0
     mov r5, 0
+    mov r6, 0
+    mov r7, 0
 
     ret
+
+; shift all events down by one, overwriting the zero'th event
+; inputs:
+; none
+; outputs:
+; none
+shift_events:
+    push r0
+    push r1
+    push r2
+    push r3
+    push r4
+
+    ; for (int i = 0; i < (event_queue_index - 1); i++) {
+    ;    event_queue[i] = event_queue[i + 1];
+    ; }
+
+    movz.8 r31, [event_queue_index]
+    mov r3, 0 ; i
+
+    ; source pointer: event_queue[i + 1]
+    mov r0, event_queue_bottom
+    mov r4, r3
+    inc r4
+    mul r4, event_size_words
+    add r0, r4
+
+    ; destination pointer: event_queue[i]
+    mov r1, event_queue_bottom
+    mov r4, r3
+    mul r4, event_size_words
+    add r1, r4
+
+    ; size: event_size_words
+    mov r2, event_size_words
+
+    call copy_memory_words
+
+    pop r4
+    pop r3
+    pop r2
+    pop r1
+    pop r0
+    ret

fox32rom.def

@@ -3,8 +3,9 @@
 ; system jump table entries
 system_vsync_handler:                     jmp [0xF1000000]
 get_mouse_position:                       jmp [0xF1000004]
-push_event:                               jmp [0xF1000008]
+new_event:                                jmp [0xF1000008]
 wait_for_event:                           jmp [0xF100000C]
+get_next_event:                           jmp [0xF1000010]
 
 ; background jump table entries
 draw_str_to_background:                   jmp [0xF1001000]

main.asm

@@ -8,7 +8,6 @@ const background_color: 0xFF414C50
     ; initialization code
 entry:
     mov rsp, system_stack
-    mov [event_stack_pointer], event_stack
 
     mov [0x000003FC], system_vsync_handler
 
@@ -110,8 +109,7 @@ draw_startup_text:
 
     ise
 event_loop:
-    halt
+    call get_next_event
-    call pop_event
 
     ; was the mouse clicked?
     cmp r0, mouse_click_event_type
@@ -183,8 +181,9 @@ mount_boot_disk:
     org.pad 0xF1000000
     data.32 system_vsync_handler
     data.32 get_mouse_position
-    data.32 push_event
+    data.32 new_event
     data.32 wait_for_event
+    data.32 get_next_event
 
     ; background jump table
     org.pad 0xF1001000

menu.asm

@@ -113,6 +113,8 @@ menu_bar_click_event:
     push r3
     push r4
     push r5
+    push r6
+    push r7
     push r28
     push r29
     push r30
@@ -156,18 +158,7 @@ menu_bar_click_event_loop:
     ;mov r1, 0xFFFFFFFF
     ;call draw_menu_bar_root_items ; close_submenu already calls this
     call close_submenu
-
+    jmp menu_bar_click_event_end
-    pop r31
-    pop r30
-    pop r29
-    pop r28
-    pop r5
-    pop r4
-    pop r3
-    pop r2
-    pop r1
-    pop r0
-    ret
 menu_bar_click_event_found_item:
     ; r30 contains the clicked root menu item (starting at 0)
     pop r0
@@ -182,13 +173,17 @@ menu_bar_click_event_found_item:
     mov r3, 0xFFFFFFFF            ; event parameter 2: hovering submenu item (or 0xFFFFFFFF for none)
     mov r4, 0
     mov r5, 0
+    mov r6, 0
+    mov r7, 0
     mov r0, submenu_update_event_type
-    call push_event
+    call new_event
-
+menu_bar_click_event_end:
     pop r31
     pop r30
     pop r29
     pop r28
+    pop r7
+    pop r6
     pop r5
     pop r4
     pop r3

mouse.asm

@@ -34,6 +34,8 @@ mouse_update:
     push r3
     push r4
     push r5
+    push r6
+    push r7
 
     mov r0, 0x8000001F            ; overlay 31: position
     in r2, 0x80000401             ; mouse position
@@ -75,8 +77,10 @@ mouse_update:
     mov r3, 0
     mov r4, 0
     mov r5, 0
+    mov r6, 0
+    mov r7, 0
     mov r0, mouse_click_event_type ; set event type to mouse type
-    call push_event
+    call new_event
     jmp mouse_update_end
 mouse_update_menu_was_clicked:
     mov r2, r1                    ; copy Y position to event parameter 1
@@ -84,9 +88,13 @@ mouse_update_menu_was_clicked:
     mov r3, 0
     mov r4, 0
     mov r5, 0
+    mov r6, 0
+    mov r7, 0
     mov r0, menu_bar_click_event_type ; set event type to menu bar click type
-    call push_event
+    call new_event
 mouse_update_end:
+    pop r7
+    pop r6
     pop r5
     pop r4
     pop r3

submenu.asm

@@ -186,6 +186,8 @@ submenu_update_event:
     push r3
     push r4
     push r5
+    push r6
+    push r7
     push r8
     push r9
 
@@ -235,8 +237,10 @@ submenu_update_event_clicked:
     mov r3, r10                   ; event parameter 2: selected submenu item
     mov r4, 0
     mov r5, 0
+    mov r6, 0
+    mov r7, 0
     mov r0, submenu_click_event_type
-    call push_event
+    call new_event
     mov r0, r1
     call close_submenu
     jmp submenu_update_event_end_no_push
@@ -247,11 +251,15 @@ submenu_update_event_end_push:
     mov r3, r10                   ; event parameter 2: hovering submenu item (or 0xFFFFFFFF for none)
     mov r4, 0
     mov r5, 0
+    mov r6, 0
+    mov r7, 0
     mov r0, submenu_update_event_type
-    call push_event
+    call new_event
 submenu_update_event_end_no_push:
     pop r9
     pop r8
+    pop r7
+    pop r6
     pop r5
     pop r4
     pop r3