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import { pointFrom, type GlobalPoint, type LocalPoint } from "@excalidraw/math";
import { THEME } from "../constants";
import type { PointSnapLine, PointerSnapLine } from "../snapping";
import type { InteractiveCanvasAppState } from "../types";
const SNAP_COLOR_LIGHT = "#ff6b6b";
const SNAP_COLOR_DARK = "#ff0000";
const SNAP_WIDTH = 1;
const SNAP_CROSS_SIZE = 2;
export const renderSnaps = (
context: CanvasRenderingContext2D,
appState: InteractiveCanvasAppState,
) => {
if (!appState.snapLines.length) {
return;
}
// in dark mode, we need to adjust the color to account for color inversion.
// Don't change if zen mode, because we draw only crosses, we want the
// colors to be more visible
const snapColor =
appState.theme === THEME.LIGHT || appState.zenModeEnabled
? SNAP_COLOR_LIGHT
: SNAP_COLOR_DARK;
// in zen mode make the cross more visible since we don't draw the lines
const snapWidth =
(appState.zenModeEnabled ? SNAP_WIDTH * 1.5 : SNAP_WIDTH) /
appState.zoom.value;
context.save();
context.translate(appState.scrollX, appState.scrollY);
for (const snapLine of appState.snapLines) {
if (snapLine.type === "pointer") {
context.lineWidth = snapWidth;
context.strokeStyle = snapColor;
drawPointerSnapLine(snapLine, context, appState);
} else if (snapLine.type === "gap") {
context.lineWidth = snapWidth;
context.strokeStyle = snapColor;
drawGapLine(
snapLine.points[0],
snapLine.points[1],
snapLine.direction,
appState,
context,
);
} else if (snapLine.type === "points") {
context.lineWidth = snapWidth;
context.strokeStyle = snapColor;
drawPointsSnapLine(snapLine, context, appState);
}
}
context.restore();
};
const drawPointsSnapLine = (
pointSnapLine: PointSnapLine,
context: CanvasRenderingContext2D,
appState: InteractiveCanvasAppState,
) => {
if (!appState.zenModeEnabled) {
const firstPoint = pointSnapLine.points[0];
const lastPoint = pointSnapLine.points[pointSnapLine.points.length - 1];
drawLine(firstPoint, lastPoint, context);
}
for (const point of pointSnapLine.points) {
drawCross(point, appState, context);
}
};
const drawPointerSnapLine = (
pointerSnapLine: PointerSnapLine,
context: CanvasRenderingContext2D,
appState: InteractiveCanvasAppState,
) => {
drawCross(pointerSnapLine.points[0], appState, context);
if (!appState.zenModeEnabled) {
drawLine(pointerSnapLine.points[0], pointerSnapLine.points[1], context);
}
};
const drawCross = <Point extends LocalPoint | GlobalPoint>(
[x, y]: Point,
appState: InteractiveCanvasAppState,
context: CanvasRenderingContext2D,
) => {
context.save();
const size =
(appState.zenModeEnabled ? SNAP_CROSS_SIZE * 1.5 : SNAP_CROSS_SIZE) /
appState.zoom.value;
context.beginPath();
context.moveTo(x - size, y - size);
context.lineTo(x + size, y + size);
context.moveTo(x + size, y - size);
context.lineTo(x - size, y + size);
context.stroke();
context.restore();
};
const drawLine = <Point extends LocalPoint | GlobalPoint>(
from: Point,
to: Point,
context: CanvasRenderingContext2D,
) => {
context.beginPath();
context.lineTo(from[0], from[1]);
context.lineTo(to[0], to[1]);
context.stroke();
};
const drawGapLine = <Point extends LocalPoint | GlobalPoint>(
from: Point,
to: Point,
direction: "horizontal" | "vertical",
appState: InteractiveCanvasAppState,
context: CanvasRenderingContext2D,
) => {
// a horizontal gap snap line
// |–––––––||–––––––|
// ^ ^ ^ ^
// \ \ \ \
// (1) (2) (3) (4)
const FULL = 8 / appState.zoom.value;
const HALF = FULL / 2;
const QUARTER = FULL / 4;
if (direction === "horizontal") {
const halfPoint = [(from[0] + to[0]) / 2, from[1]];
// (1)
if (!appState.zenModeEnabled) {
drawLine(
pointFrom(from[0], from[1] - FULL),
pointFrom(from[0], from[1] + FULL),
context,
);
}
// (3)
drawLine(
pointFrom(halfPoint[0] - QUARTER, halfPoint[1] - HALF),
pointFrom(halfPoint[0] - QUARTER, halfPoint[1] + HALF),
context,
);
drawLine(
pointFrom(halfPoint[0] + QUARTER, halfPoint[1] - HALF),
pointFrom(halfPoint[0] + QUARTER, halfPoint[1] + HALF),
context,
);
if (!appState.zenModeEnabled) {
// (4)
drawLine(
pointFrom(to[0], to[1] - FULL),
pointFrom(to[0], to[1] + FULL),
context,
);
// (2)
drawLine(from, to, context);
}
} else {
const halfPoint = [from[0], (from[1] + to[1]) / 2];
// (1)
if (!appState.zenModeEnabled) {
drawLine(
pointFrom(from[0] - FULL, from[1]),
pointFrom(from[0] + FULL, from[1]),
context,
);
}
// (3)
drawLine(
pointFrom(halfPoint[0] - HALF, halfPoint[1] - QUARTER),
pointFrom(halfPoint[0] + HALF, halfPoint[1] - QUARTER),
context,
);
drawLine(
pointFrom(halfPoint[0] - HALF, halfPoint[1] + QUARTER),
pointFrom(halfPoint[0] + HALF, halfPoint[1] + QUARTER),
context,
);
if (!appState.zenModeEnabled) {
// (4)
drawLine(
pointFrom(to[0] - FULL, to[1]),
pointFrom(to[0] + FULL, to[1]),
context,
);
// (2)
drawLine(from, to, context);
}
}
};
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