[Decompilation] [th05] Lasers: Update function

In which the shrink types """conveniently""" use a signed comparison
that effectively limits their width to 127 pixels, which forces a
shrink/nonshrink distinction upon the entire rest of the code. 🙄

Part of P0228, funded by [Anonymous] and nrook.

th05/main/boss/b1.cpp

@@ -299,7 +299,7 @@ void near pattern_dense_spreads_and_random_balls_within_laser_walls(void)
 		laser_template.coords.origin = boss.pos.cur;
 		laser_template.coords.angle = (-0x40 + 0x20);
 		laser_template.col = 8;
-		laser_template.coords.width = 8;
+		laser_template.coords.width.nonshrink = 8;
 		laser_manual_fixed_spawn(X_RIGHT);
 
 		laser_template.coords.angle = (-0x40 - 0x20);

th05/main/boss/b6.cpp

@@ -513,7 +513,7 @@ void near pattern_devil(void)
 	// Laser activation
 	if((boss.hp <= HP_PHASE_10_DEVIL_LASER) || (boss.phase_frame >= 1800)) {
 		if(laser_grow_delay == 0) {
-			laser_template.coords.width = 6;
+			laser_template.coords.width.nonshrink = 6;
 			laser_template.coords.angle = 0x40;
 			laser_template.col = 0xE;
 

th05/main/bullet/laser.cpp

@@ -8,10 +8,122 @@ extern "C" {
 #include "th04/math/vector.hpp"
 #include "th04/snd/snd.h"
 #include "th04/main/playfld.hpp"
+#include "th04/main/bullet/clearzap.hpp"
 #include "th05/main/playperf.hpp"
 }
 #include "th05/main/bullet/laser.hpp"
 
+// Segment 1 (as allocated in the header)
+// ---------
+
+// ZUN bloat: Needed to circumvent 16-bit promotion in comparisons.
+inline int8_t laser_width_min(void) {
+	return 1;
+}
+
+void near lasers_update(void)
+{
+	#define shootout_update(laser) { \
+		if(laser->coords.starts_at_distance < to_sp(LASER_DISTANCE_MAX)) { \
+			laser->coords.ends_at_distance.v += laser->shootout_speed.v; \
+		} \
+		if(laser->age >= laser->active_at_age.moveout) { \
+			laser->coords.starts_at_distance.v += laser->shootout_speed.v; \
+		} \
+	}
+
+	Laser near *laser;
+	int i;
+	for((laser = lasers, i = 0); i < LASER_COUNT; (i++, laser++)) {
+		if(laser->flag == LF_FREE) {
+			continue;
+		}
+
+		if(bullet_clear_time || bullet_zap.active) {
+			if(laser->flag == LF_SHOOTOUT) {
+				laser->flag = LF_SHOOTOUT_DECAY;
+				laser->shootout_speed.v /= 2;
+			}
+		}
+
+		switch(laser->flag) {
+		case LF_SHOOTOUT:
+			shootout_update(laser);
+			laser_hittest(*laser);
+			break;
+
+		case LF_FIXED_WAIT_TO_GROW:
+			if(laser->active_at_age.grow > 0) {
+				if(laser->age >= laser->active_at_age.grow) {
+					// laser->flag = LF_FIXED_GROW;
+					static_cast<uint8_t>(laser->flag)++;
+					snd_se_play(6);
+				}
+			}
+			break;
+
+		case LF_FIXED_GROW:
+			if(laser->age & 1) {
+				laser->coords.width.nonshrink += 2;
+			}
+			if(laser->coords.width.nonshrink >= laser->grow_to_width) {
+				// laser->flag = LF_FIXED_ACTIVE;
+				static_cast<uint8_t>(laser->flag)++;
+			}
+			break;
+
+		case LF_FIXED_ACTIVE:
+			laser_hittest(*laser);
+			if(laser->shrink_at_age > 0) {
+				if(laser->age >= laser->shrink_at_age) {
+					// laser->flag = LF_FIXED_SHRINK;
+					static_cast<uint8_t>(laser->flag)++;
+				}
+			}
+			break;
+
+		case LF_FIXED_SHRINK:
+			if(laser->age & 1) {
+				// MODDERS: The necessary clamp to 0 here is caught by the
+				// signed comparison below.
+				laser->coords.width.shrink -= 2;
+			}
+			if(laser->coords.width.shrink < laser_width_min()) {
+				laser->flag = LF_FREE;
+			}
+			break;
+
+		case LF_FIXED_SHRINK_AND_WAIT_TO_GROW:
+			if(laser->age & 1) {
+				// MODDERS: See above… except that the signed comparison
+				// wouldn't even have been needed here, as the condition is
+				// `true` for both 1 and 0.
+				laser->coords.width.shrink -= 2;
+			}
+			if(laser->coords.width.shrink <= laser_width_min()) {
+				laser->flag = LF_FIXED_WAIT_TO_GROW;
+				laser->age = 0;
+			}
+			break;
+
+		case LF_SHOOTOUT_DECAY:
+			shootout_update(laser);
+			laser->coords.width.nonshrink += 2;
+			if(
+				laser->coords.width.nonshrink >=
+				LASER_SHOOTOUT_DECAY_WIDTH_MAX
+			) {
+				laser->flag = LF_FREE;
+			}
+			break;
+		}
+		laser->age++;
+	}
+
+	#undef shootout_update
+}
+// ---------
+
 // Segment 3 (as allocated in the header)
 // ---------
 
@@ -33,7 +145,7 @@ void near lasers_shootout_add(void)
 		laser->col = laser_template.col;
 		laser->shootout_speed.v = speed;
 		laser->grow_to_width = 6;
-		laser->coords.width = 6;
+		laser->coords.width.nonshrink = 6;
 		laser->coords.angle = laser_template.coords.angle;
 		vector2_at(
 			laser->coords.origin,
@@ -57,8 +169,8 @@ void pascal near laser_fixed_spawn(int slot)
 	laser.active_at_age.grow = laser_template.active_at_age.grow;
 	laser.shrink_at_age = laser_template.shrink_at_age;
 	laser.col = laser_template.col;
-	laser.grow_to_width = laser_template.coords.width;
-	laser.coords.width = 1;
+	laser.grow_to_width = laser_template.coords.width.nonshrink;
+	laser.coords.width.nonshrink = 1;
 	laser.coords.angle = laser_template.coords.angle;
 	snd_se_play(5);
 }
@@ -73,8 +185,8 @@ void pascal near laser_manual_fixed_spawn(int slot)
 	laser.active_at_age.grow = -1;
 	laser.shrink_at_age = -1;
 	laser.col = laser_template.col;
-	laser.coords.width = 1;
-	laser.grow_to_width = laser_template.coords.width;
+	laser.coords.width.nonshrink = 1;
+	laser.grow_to_width = laser_template.coords.width.nonshrink;
 	laser.coords.angle = laser_template.coords.angle;
 	snd_se_play(5);
 }
@@ -93,10 +205,10 @@ void pascal near laser_stop(int slot)
 	if(lasers[slot].flag == LF_FIXED_ACTIVE) {
 		lasers[slot].flag = LF_FIXED_SHRINK;
 	} else if (lasers[slot].flag == LF_SHOOTOUT) {
-		lasers[slot].flag = LF_DECAY;
+		lasers[slot].flag = LF_SHOOTOUT_DECAY;
 	} else if (
 		(lasers[slot].flag != LF_FIXED_SHRINK) &&
-		(lasers[slot].flag != LF_DECAY)
+		(lasers[slot].flag != LF_SHOOTOUT_DECAY)
 	) {
 		lasers[slot].flag = LF_FREE;
 	}

th05/main/bullet/laser.hpp

@@ -1,6 +1,9 @@
 #define LASER_DISTANCE_MIN 16.0f
 #define LASER_DISTANCE_MAX 550.0f /* Far away enough? */
 
+static const pixel_t LASER_SHOOTOUT_DECAY_WIDTH = 6;
+static const pixel_t LASER_SHOOTOUT_DECAY_WIDTH_MAX = 28;
+
 enum laser_flag_t {
 	LF_FREE = 0,
 	LF_SHOOTOUT = 1,
@@ -11,9 +14,15 @@ enum laser_flag_t {
 	// player on contact.
 	LF_FIXED_ACTIVE = 4,
 
+	// Fixed laser will shrink to a width of 1 and then either be removed
+	// (LF_FIXED_SHRINK) or go back to LF_FIXED_WAIT_TO_GROW with its [age]
+	// reset to 0 (LF_FIXED_SHRINK_AND_WAIT_TO_GROW).
 	LF_FIXED_SHRINK = 5,
 	LF_FIXED_SHRINK_AND_WAIT_TO_GROW = 6,
-	LF_DECAY = 7,
+
+	LF_SHOOTOUT_DECAY = 7,
+
+	_laser_flag_t_FORCE_UINT8 = 0xFF
 };
 
 struct laser_coords_t {
@@ -25,7 +34,22 @@ struct laser_coords_t {
 	Subpixel ends_at_distance;
 
 	unsigned char angle;
-	unsigned char width; // pixel_t
+
+	// In pixels.
+	union {
+		// ZUN bug: LF_FIXED_SHRINK and LF_FIXED_SHRINK_AND_WAIT_TO_GROW are
+		// effectively limited to a maximum width of 127 pixels due to an
+		// implementation convenience in their update code. For larger values,
+		// their shrink animation wouldn't play, and the laser will transition
+		// to its next flag immediately.
+		int8_t shrink;
+
+		// Other types have no limit besides the 8-bit one inherent to the
+		// type. Shootout lasers should probably still be kept below
+		// LASER_SHOOTOUT_DECAY_WIDTH_MAX though, as any larger value would
+		// skip the decay animation.
+		uint8_t nonshrink;
+	} width;
 };
 
 struct Laser {

th05/main/bullet/laser_rh.cpp

@@ -164,7 +164,7 @@ bool16 pascal near laser_render_ray(const laser_coords_t near& coords)
 		SpaceChangingPoint bp[8];
 	} ps;
 
-	v_length_low = coords.width;
+	v_length_low = coords.width.nonshrink;
 	v_length_high = 0;
 	v_length <<= (SUBPIXEL_BITS - 1);
 

th05/main/bullet/lasers[bss].asm

@@ -1,11 +1,7 @@
 LF_FREE = 0
-LF_SHOOTOUT = 1
 LF_FIXED_WAIT_TO_GROW = 2
-LF_FIXED_GROW = 3
-LF_FIXED_ACTIVE = 4
-LF_FIXED_SHRINK = 5
 LF_FIXED_SHRINK_AND_WAIT_TO_GROW = 6
-LF_DECAY = 7
+LF_SHOOTOUT_DECAY = 7
 
 laser_coords_t struc
 	origin            	Point <?>

th05/main/bullet/lasers_update_render.asm

@@ -1,179 +1,5 @@
 	@LASER_RENDER_RAY$QRX14LASER_COORDS_T procdesc pascal near \
 		coords:word
-	@LASER_HITTEST$QR5LASER procdesc pascal near \
-		laser:word
-
-public @lasers_update$qv
-@lasers_update$qv proc near
-	push	bp
-	mov	bp, sp
-	push	si
-	push	di
-	mov	si, offset _lasers
-	xor	di, di
-	jmp	@@more?
-
-@@loop:
-	cmp	[si+laser_t.flag], LF_FREE
-	jz	@@next
-	cmp	_bullet_clear_time, 0
-	jnz	short @@shootout
-	cmp	_bullet_zap_active, 0
-	jz	short @@switch
-
-@@shootout:
-	cmp	[si+laser_t.flag], LF_SHOOTOUT
-	jnz	short @@switch
-	mov	[si+laser_t.flag], LF_DECAY
-	mov	ax, [si+laser_t.shootout_speed]
-	cwd
-	sub	ax, dx
-	sar	ax, 1
-	mov	[si+laser_t.shootout_speed], ax
-
-@@switch:
-	mov	al, [si+laser_t.flag]
-	mov	ah, 0
-	dec	ax
-	mov	bx, ax
-	cmp	bx, 6
-	ja	@@age_inc
-	add	bx, bx
-	jmp	cs:lasers_update_switch[bx]
-
-laser_update_shootout:
-	cmp	[si+laser_t.coords.starts_at_distance], (550 shl 4)
-	jge	short loc_FC52
-	mov	ax, [si+laser_t.shootout_speed]
-	add	[si+laser_t.coords.ends_at_distance], ax
-
-loc_FC52:
-	mov	ax, [si+laser_t.LASER_age]
-	cmp	ax, [si+laser_t.moveout_at_age]
-	jl	short loc_FC60
-	mov	ax, [si+laser_t.shootout_speed]
-	add	[si+laser_t.coords.starts_at_distance], ax
-
-loc_FC60:
-	call	@laser_hittest$qr5Laser pascal, si
-	jmp	@@age_inc
-; ---------------------------------------------------------------------------
-
-laser_update_fixed_wait_to_grow:
-	cmp	[si+laser_t.grow_at_age], 0
-	jle	@@age_inc
-	mov	ax, [si+laser_t.LASER_age]
-	cmp	ax, [si+laser_t.grow_at_age]
-	jl	@@age_inc
-	inc	[si+laser_t.flag]
-	call	snd_se_play pascal, 6
-	jmp	@@age_inc
-; ---------------------------------------------------------------------------
-
-laser_update_fixed_grow:
-	test	byte ptr [si+laser_t.LASER_age], 1
-	jz	short @@grow_step
-	mov	al, [si+laser_t.coords.LASER_width]
-	add	al, 2
-	mov	[si+laser_t.coords.LASER_width], al
-
-@@grow_step:
-	mov	al, [si+laser_t.coords.LASER_width]
-	cmp	al, [si+laser_t.grow_to_width]
-	jb	short @@age_inc
-	jmp	short @@next_mode
-; ---------------------------------------------------------------------------
-
-laser_update_fixed_active:
-	call	@laser_hittest$qr5Laser pascal, si
-	cmp	[si+laser_t.shrink_at_age], 0
-	jle	short @@age_inc
-	mov	ax, [si+laser_t.LASER_age]
-	cmp	ax, [si+laser_t.shrink_at_age]
-	jl	short @@age_inc
-
-@@next_mode:
-	inc	[si+laser_t.flag]
-	jmp	short @@age_inc
-; ---------------------------------------------------------------------------
-
-laser_update_fixed_shrink:
-	test	byte ptr [si+laser_t.LASER_age], 1
-	jz	short @@delete?
-	mov	al, [si+laser_t.coords.LASER_width]
-	add	al, -2
-	mov	[si+laser_t.coords.LASER_width], al
-
-@@delete?:
-	cmp	[si+laser_t.coords.LASER_width], 1
-	jge	short @@age_inc
-	jmp	short @@delete
-; ---------------------------------------------------------------------------
-
-laser_update_fixed_shrink_and_wait_to_grow:
-	test	byte ptr [si+laser_t.LASER_age], 1
-	jz	short @@shrink_and_wait_to_grow_step
-	mov	al, [si+laser_t.coords.LASER_width]
-	add	al, -2
-	mov	[si+laser_t.coords.LASER_width], al
-
-@@shrink_and_wait_to_grow_step:
-	cmp	[si+laser_t.coords.LASER_width], 1
-	jg	short @@age_inc
-	mov	[si+laser_t.flag], LF_FIXED_WAIT_TO_GROW
-	mov	[si+laser_t.LASER_age], 0
-	jmp	short @@age_inc
-; ---------------------------------------------------------------------------
-
-laser_update_decay:
-	cmp	[si+laser_t.coords.starts_at_distance], (550 shl 4)
-	jge	short loc_FCF4
-	mov	ax, [si+laser_t.shootout_speed]
-	add	[si+laser_t.coords.ends_at_distance], ax
-
-loc_FCF4:
-	mov	ax, [si+laser_t.LASER_age]
-	cmp	ax, [si+laser_t.moveout_at_age]
-	jl	short loc_FD02
-	mov	ax, [si+laser_t.shootout_speed]
-	add	[si+laser_t.coords.starts_at_distance], ax
-
-loc_FD02:
-	mov	al, [si+laser_t.coords.LASER_width]
-	add	al, 2
-	mov	[si+laser_t.coords.LASER_width], al
-	cmp	[si+laser_t.coords.LASER_width], 28
-	jb	short @@age_inc
-
-@@delete:
-	mov	[si+laser_t.flag], LF_FREE
-
-@@age_inc:
-	inc	[si+laser_t.LASER_age]
-
-@@next:
-	inc	di
-	add	si, size laser_t
-
-@@more?:
-	cmp	di, LASER_COUNT
-	jl	@@loop
-	pop	di
-	pop	si
-	pop	bp
-	retn
-@lasers_update$qv endp
-
-; ---------------------------------------------------------------------------
-lasers_update_switch	label word
-	dw offset laser_update_shootout
-	dw offset laser_update_fixed_wait_to_grow
-	dw offset laser_update_fixed_grow
-	dw offset laser_update_fixed_active
-	dw offset laser_update_fixed_shrink
-	dw offset laser_update_fixed_shrink_and_wait_to_grow
-	dw offset laser_update_decay
-; ---------------------------------------------------------------------------
 
 public @lasers_render$qv
 @lasers_render$qv	proc near
@@ -217,7 +43,7 @@ public @lasers_render$qv
 	sar	ax, 4
 	add	ax, 16
 	mov	[bp+@@draw_y], ax
-	cmp	[si+laser_t.flag], LF_DECAY
+	cmp	[si+laser_t.flag], LF_SHOOTOUT_DECAY
 	jz	@@decay
 	cmp	[bp+@@radius], 2
 	jnb	short @@draw_outer_circle?

th05_main.asm

@@ -4368,6 +4368,8 @@ loc_FBF7:
 		leave
 		retn
 sub_FAA3	endp
+
+	@lasers_update$qv procdesc near
 main__TEXT	ends
 
 PLAYFLD_TEXT	segment	byte public 'CODE' use16