read joypad in vbl so that inputs are more reactive

Code/edit.asm

@@ -2,11 +2,13 @@ INCLUDE "hardware.inc"
 
 Section "Joypad memory", HRAM
 ; Bits 0..7 are A, B, Select, Start, Right, Left, Up, Down
-JoypadDown: ds 1
 JoypadPressed: ds 1
+JoypadWasPressed: ds 1
+JoypadDown: ds 1
 
-SECTION "Update joypad", ROM0
-UpdateJoypad:
+EXPORT ReadJoypad
+SECTION "Read Joypad", ROM0
+ReadJoypad:
 	; read directions
 	ld a, P1F_5
 	ldh [rP1], a 
@@ -32,22 +34,29 @@ UpdateJoypad:
 	or a, b
 	cpl
 
-	; backup all buttons in B
-	ld b, a
-	
-	; store just pressed buttons
-	ldh a, [JoypadPressed]
-	cpl 
-	and a, b
-	ldh [JoypadDown], a
-	
 	; store currently pressed buttons
-	ld a, b
 	ldh [JoypadPressed], a
 
 	; reset joypad
 	ld a, $30
 	ldh [rP1], a
+
+	ret
+
+SECTION "Update joypad", ROM0
+UpdateJoypad:	
+	; compute & store just pressed buttons
+	ldh a, [JoypadPressed]
+	ld b, a
+	ldh a, [JoypadWasPressed]
+	cpl 
+	and a, b
+	ldh [JoypadDown], a
+	
+	; update was pressed
+	ld a, b
+	ldh [JoypadWasPressed], a
+	
 	ret
 
 Section "Edit memory", HRAM
@@ -64,6 +73,7 @@ InitEdit:
 	xor a
 	ldh [JoypadDown], a
 	ldh [JoypadPressed], a
+	ldh [JoypadWasPressed], a
 	ret
 	
 

Code/render.asm

@@ -12,7 +12,11 @@ Rendered: ds 2      ; progressing pointer in old buffer
 
 SECTION "V-Blank Interrupt Handler", ROM0[$40]
 VBlankInterruptHandler:
-	jr LCDStatInterruptHandler
+	; save registers
+	push af
+	push bc
+	call ReadJoypad
+	jr LCDStatInterruptHandler.start
 
 SECTION "LCD Stat Interrupt Handler", ROM0[$48]
 LCDStatInterruptHandler:
@@ -20,6 +24,7 @@ LCDStatInterruptHandler:
 	push af
 	push bc
 
+.start    
 	; check there are tiles to render
 	ldh a, [LinesLeft]
 	or a