add fx module: screen fade, flash, shake and tone

2 files changed, 302 insertions, 0 deletions

diff --git a/kon/konfx.c b/kon/konfx.c
new file mode 100644
index 0000000..abbc7ec
--- /dev/null
+++ b/kon/konfx.c
@@ -0,0 +1,227 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * konfx.c
+ *
+ * Copyright (c) 2026 KonAki
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "konfx.h"
+
+#include <math.h>
+#include <string.h>
+
+#define PI 3.14159265358979f
+
+static float numberOr0(float v)
+{
+	return v == v && v - v == 0.0f ? v : 0.0f;
+}
+
+static int clampInt(float v, int lo, int hi)
+{
+	if (!(v > (float)lo)) return lo;
+	if (v > (float)hi) return hi;
+	return (int)floorf(v + 0.5f);
+}
+
+/*** state ***/
+
+void kon_screenfxInit(kon_screenfx_t *fx)
+{
+	kon_screenfx_t zero = {0};
+
+	*fx = zero;
+	kon_tweenSet(&fx->fade, 0.0f);
+	kon_tweenSet(&fx->flash, 0.0f);
+	kon_tweenSet(&fx->tone[0], 0.0f);
+	kon_tweenSet(&fx->tone[1], 0.0f);
+	kon_tweenSet(&fx->tone[2], 0.0f);
+	kon_tweenSet(&fx->tone[3], 0.0f);
+}
+
+void kon_screenfxFade(kon_screenfx_t *fx, uint32_t color, float alpha, float seconds, kon_ease_t ease)
+{
+	fx->fadeColor = color & 0x00FFFFFFu;
+	kon_tweenTo(&fx->fade, numberOr0(alpha), seconds, ease);
+}
+
+void kon_screenfxFlash(kon_screenfx_t *fx, uint32_t color, float seconds)
+{
+	fx->flashColor = color & 0x00FFFFFFu;
+	kon_tweenStart(&fx->flash, (float)(color >> 24) / 255.0f, 0.0f, seconds, KON_EASE_LINEAR);
+}
+
+void kon_screenfxShake(kon_screenfx_t *fx, float powerX, float powerY, float hz, float seconds)
+{
+	fx->shakeX = numberOr0(powerX);
+	fx->shakeY = numberOr0(powerY);
+	fx->shakeHz = numberOr0(hz);
+	fx->shakeTime = 0.0f;
+	fx->shakeDuration = seconds > 0.0f ? numberOr0(seconds) : 0.0f;
+}
+
+void kon_screenfxTone(kon_screenfx_t *fx, int r, int g, int b, int gray, float seconds, kon_ease_t ease)
+{
+	kon_tweenTo(&fx->tone[0], (float)r, seconds, ease);
+	kon_tweenTo(&fx->tone[1], (float)g, seconds, ease);
+	kon_tweenTo(&fx->tone[2], (float)b, seconds, ease);
+	kon_tweenTo(&fx->tone[3], (float)gray, seconds, ease);
+}
+
+void kon_screenfxUpdate(kon_screenfx_t *fx, float dt)
+{
+	int i;
+
+	kon_tweenStep(&fx->fade, dt);
+	kon_tweenStep(&fx->flash, dt);
+	for (i = 0; i < 4; i++) kon_tweenStep(&fx->tone[i], dt);
+	if (fx->shakeTime < fx->shakeDuration && dt > 0.0f) {
+		fx->shakeTime += dt;
+		if (fx->shakeTime > fx->shakeDuration) fx->shakeTime = fx->shakeDuration;
+	}
+}
+
+int kon_screenfxBusy(const kon_screenfx_t *fx)
+{
+	int i;
+
+	if (!kon_tweenDone(&fx->fade) || !kon_tweenDone(&fx->flash) || fx->shakeTime < fx->shakeDuration) return 1;
+	for (i = 0; i < 4; i++) {
+		if (!kon_tweenDone(&fx->tone[i])) return 1;
+	}
+	return 0;
+}
+
+void kon_screenfxOffset(const kon_screenfx_t *fx, int *x, int *y)
+{
+	float left, wave;
+
+	*x = *y = 0;
+	if (!(fx->shakeTime < fx->shakeDuration)) return;
+	left = 1.0f - fx->shakeTime / fx->shakeDuration;
+	wave = sinf(2.0f * PI * fx->shakeHz * fx->shakeTime) * left;
+	*x = clampInt(wave * fx->shakeX, -100000, 100000);
+	*y = clampInt(wave * fx->shakeY, -100000, 100000);
+}
+
+/*** passes ***/
+
+static void tone(const kon_screenfx_t *fx, kon_framebuffer_t *fb)
+{
+	int add[3], gray = clampInt(kon_tweenValue(&fx->tone[3]), 0, 255), i;
+	size_t n = (size_t)fb->width * (size_t)fb->height, p;
+
+	for (i = 0; i < 3; i++) add[i] = clampInt(kon_tweenValue(&fx->tone[i]), -255, 255);
+	if (!add[0] && !add[1] && !add[2] && !gray) return;
+
+	for (p = 0; p < n; p++) {
+		uint32_t c = fb->data[p];
+		int ch[3], k;
+
+		ch[0] = (int)((c >> 16) & 0xFF);
+		ch[1] = (int)((c >> 8) & 0xFF);
+		ch[2] = (int)(c & 0xFF);
+		if (gray) {
+			int lum = (ch[0] * 299 + ch[1] * 587 + ch[2] * 114) / 1000;
+
+			for (k = 0; k < 3; k++) ch[k] += (lum - ch[k]) * gray / 255;
+		}
+		for (k = 0; k < 3; k++) {
+			ch[k] += add[k];
+			if (ch[k] < 0) ch[k] = 0;
+			if (ch[k] > 255) ch[k] = 255;
+		}
+		fb->data[p] = (c & 0xFF000000u) | ((uint32_t)ch[0] << 16) | ((uint32_t)ch[1] << 8) | (uint32_t)ch[2];
+	}
+}
+
+/* moves the whole picture, the edge pixels are repeated into what is uncovered */
+static void shift(kon_framebuffer_t *fb, int dx, int dy)
+{
+	int w = fb->width, h = fb->height, y;
+
+	if (w < 1 || h < 1) return;
+	if (dx >= w) dx = w - 1;
+	if (dx <= -w) dx = -w + 1;
+	if (dy >= h) dy = h - 1;
+	if (dy <= -h) dy = -h + 1;
+	if (!dx && !dy) return;
+
+	if (dy > 0) {
+		for (y = h - 1; y >= 0; y--) {
+			int from = y - dy < 0 ? 0 : y - dy;
+
+			if (from != y) memcpy(&fb->data[(size_t)y * (size_t)w], &fb->data[(size_t)from * (size_t)w], (size_t)w * sizeof fb->data[0]);
+		}
+	} else if (dy < 0) {
+		for (y = 0; y < h; y++) {
+			int from = y - dy > h - 1 ? h - 1 : y - dy;
+
+			if (from != y) memcpy(&fb->data[(size_t)y * (size_t)w], &fb->data[(size_t)from * (size_t)w], (size_t)w * sizeof fb->data[0]);
+		}
+	}
+	if (!dx) return;
+	for (y = 0; y < h; y++) {
+		uint32_t *row = &fb->data[(size_t)y * (size_t)w];
+		int i;
+
+		if (dx > 0) {
+			memmove(row + dx, row, (size_t)(w - dx) * sizeof row[0]);
+			for (i = 0; i < dx; i++) row[i] = row[dx];
+		} else {
+			memmove(row, row - dx, (size_t)(w + dx) * sizeof row[0]);
+			for (i = w + dx; i < w; i++) row[i] = row[w + dx - 1];
+		}
+	}
+}
+
+static void cover(kon_framebuffer_t *fb, uint32_t color, float alpha)
+{
+	uint32_t a;
+
+	if (!(alpha > 0.0f)) return;
+	if (alpha > 1.0f) alpha = 1.0f;
+	a = (uint32_t)(alpha * 255.0f + 0.5f);
+	if (a) kon_fillRectangle(fb, 0, 0, fb->width, fb->height, (a << 24) | (color & 0x00FFFFFFu));
+}
+
+void kon_screenfxApplyScene(const kon_screenfx_t *fx, kon_framebuffer_t *fb)
+{
+	int x, y;
+
+	if (!fb) return;
+	tone(fx, fb);
+	kon_screenfxOffset(fx, &x, &y);
+	shift(fb, x, y);
+}
+
+void kon_screenfxApplyOverlay(const kon_screenfx_t *fx, kon_framebuffer_t *fb)
+{
+	if (!fb) return;
+	cover(fb, fx->flashColor, kon_tweenValue(&fx->flash));
+	cover(fb, fx->fadeColor, kon_tweenValue(&fx->fade));
+}
+
+void kon_screenfxApply(const kon_screenfx_t *fx, kon_framebuffer_t *fb)
+{
+	kon_screenfxApplyScene(fx, fb);
+	kon_screenfxApplyOverlay(fx, fb);
+}
diff --git a/kon/konfx.h b/kon/konfx.h
new file mode 100644
index 0000000..0261b59
--- /dev/null
+++ b/kon/konfx.h
@@ -0,0 +1,75 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * konfx.h
+ *
+ * Copyright (c) 2026 KonAki
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#ifndef KONFX_H
+#define KONFX_H
+
+#include "konsofren.h"
+#include "kon2d.h"
+
+/*** definition ***/
+
+/* the effects that go over a whole picture: a fade to a colour, a flash, a shake and a tone. they are done to the pixels after
+   the scene is drawn, so they work on anything, a map, a stage, a 3D view. start them with the functions below, call kon_screenfxUpdate
+   every frame and then kon_screenfxApply on the framebuffer when the scene is drawn. keep the struct around, it holds the state */
+typedef struct kon_screenfx {
+	kon_tween_t fade;
+	uint32_t fadeColor;
+	kon_tween_t flash;
+	uint32_t flashColor;
+	kon_tween_t tone[4]; /* red, green, blue, gray */
+	float shakeX, shakeY, shakeHz, shakeTime, shakeDuration;
+} kon_screenfx_t;
+
+void kon_screenfxInit(kon_screenfx_t *fx);
+
+/* fades to color (alpha is ignored) until it covers alpha of the picture, 1 is all of it, 0 is back to normal */
+void kon_screenfxFade(kon_screenfx_t *fx, uint32_t color, float alpha, float seconds, kon_ease_t ease);
+
+/* covers the picture with color at the strength of its alpha and lets it go in seconds */
+void kon_screenfxFlash(kon_screenfx_t *fx, uint32_t color, float seconds);
+
+/* shakes by up to powerX and powerY pixels, hz times a second, getting weaker until it stops after seconds */
+void kon_screenfxShake(kon_screenfx_t *fx, float powerX, float powerY, float hz, float seconds);
+
+/* r, g, b from -255 to 255 are added to every pixel, gray from 0 to 255 takes the colour out, 255 is black and white.
+   all zero is no change. the same as RPG Maker's screen tone */
+void kon_screenfxTone(kon_screenfx_t *fx, int r, int g, int b, int gray, float seconds, kon_ease_t ease);
+
+void kon_screenfxUpdate(kon_screenfx_t *fx, float dt);
+
+/* 1 while something is still changing, for a script that waits for it */
+int kon_screenfxBusy(const kon_screenfx_t *fx);
+
+/* how far the picture is shifted right now, for a game that would rather move its camera than the pixels */
+void kon_screenfxOffset(const kon_screenfx_t *fx, int *x, int *y);
+
+/* tone and shake, then flash and fade. two halves so a text box can be drawn between them and stay still and clear,
+   kon_screenfxApply is both for when it should all be covered */
+void kon_screenfxApplyScene(const kon_screenfx_t *fx, kon_framebuffer_t *fb);
+void kon_screenfxApplyOverlay(const kon_screenfx_t *fx, kon_framebuffer_t *fb);
+void kon_screenfxApply(const kon_screenfx_t *fx, kon_framebuffer_t *fb);
+
+#endif