[Decompilation] [th01] Boss entities: Clamped movement + unblitting +…

… blitting

A function which does so many individual things that I can't even
summarize it in a comment without spelling out each line of code. And
then, this entire clamped movement system is only used for Kikuri's
soul sprites. The usage code for every other entity just parties on
the [cur_left] and [cur_top] members, and passes a delta of (0, 0) to
this function. 🤷

Part of P0108, funded by Yanga.

Research/Borland C++ decompilation.md

@@ -40,6 +40,7 @@ where the scalar-type variable is declared in relation to them.
 | `ADD [m8], imm8` | Only achievable through a C++ method operating on a  member? |
 | `MOV AL, [m8]`<br />`ADD AL, imm8`<br />`MOV [m8], AL` | Opposite; *not* an inlined function |
 | `CWD`<br />`SUB AX, DX`<br />`SAR AX, 1` | `AX / 2`, `AX` is *int* |
+| `MOV [new_var], AX`<br />`CWD`<br />`XOR AX, DX`<br />`SUB AX, DX` | `abs(AX)`, defined in `<stdlib.h>`. `AX` is *int* |
 
 ### Arithmetic on a register *after* assigning it to a variable?
 

th01/main/boss/entity.cpp

@@ -528,3 +528,32 @@ void CBossEntity::sloppy_unput() const
 {
 	egc_copy_rect_1_to_0_16(cur_left, cur_top, (vram_w * BYTE_DOTS), h);
 }
+
+void CBossEntity::move_lock_unput_and_put_8(
+	int, int delta_x, int delta_y, int lock_frames
+)
+{
+	if(move_lock_frame == 0) {
+		move(delta_x, delta_y);
+
+		int unput_left = (prev_delta_x > 0)
+			? ((prev_left / BYTE_DOTS) * BYTE_DOTS)
+			: (((cur_left / BYTE_DOTS) * BYTE_DOTS) + (vram_w * BYTE_DOTS));
+		egc_copy_rect_1_to_0_16(unput_left, prev_top, 8, h);
+
+		int unput_top = (cur_top > prev_top)
+			? prev_top
+			: (cur_top + h);
+		egc_copy_rect_1_to_0_16(
+			prev_left, unput_top, (vram_w << 3), abs(cur_top - prev_top)
+		);
+
+		unput_and_put_8(cur_left, cur_top, bos_image);
+
+		move_lock_frame = 1;
+	} else if(move_lock_frame >= lock_frames) {
+		move_lock_frame = 0;
+	} else {
+		move_lock_frame++;
+	}
+}

th01/main/boss/entity.hpp

@@ -112,6 +112,31 @@ class CBossEntity {
 
 	/// Movement
 	/// --------
+protected:
+	void move(const int &delta_x, const int &delta_y) {
+		prev_delta_x = delta_x;
+		prev_delta_y = delta_y;
+		prev_left = cur_left;
+		prev_top = cur_top;
+
+		cur_left += prev_delta_x;
+		if(move_clamp.left > cur_left) {
+			cur_left = move_clamp.left;
+		}
+		if(move_clamp.right < cur_left) {
+			cur_left = move_clamp.right;
+		}
+
+		cur_top += prev_delta_y;
+		if(cur_top < move_clamp.top) {
+			cur_top = move_clamp.top;
+		}
+		if(cur_top > move_clamp.bottom) {
+			cur_top = move_clamp.bottom;
+		}
+	}
+
+public:
 	// Sets [cur_left], [cur_top], [unknown], and the [move_clamp] area.
 	void pos_set(
 		int left,
@@ -122,5 +147,11 @@ class CBossEntity {
 		int move_clamp_top,
 		int move_clamp_bottom
 	);
+
+	// (Just read the actual function code, it's impossible to summarize
+	// without spelling every single line here.)
+	void move_lock_unput_and_put_8(
+		int unused, int delta_x, int delta_y, int lock_frames
+	);
 	/// --------
 };