blob: 7ce182bc5b3f6673d73db3e73e94eaf9c29852d4 [file] [log] [blame]
// Copyright (C) 2018 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
const LOADING_TEXT = 'Loading...';
let LOADING_TEXT_WIDTH = 0;
/**
* Checker board the range [leftPx, rightPx].
*/
export function checkerboard(
ctx: CanvasRenderingContext2D,
heightPx: number,
leftPx: number,
rightPx: number): void {
const widthPx = rightPx - leftPx;
ctx.font = '12px Roboto Condensed';
ctx.fillStyle = '#eee';
ctx.fillRect(leftPx, 0, widthPx, heightPx);
ctx.fillStyle = '#666';
const oldBaseline = ctx.textBaseline;
ctx.textBaseline = 'middle';
if (LOADING_TEXT_WIDTH === 0) {
LOADING_TEXT_WIDTH = ctx.measureText(LOADING_TEXT).width;
}
if (LOADING_TEXT_WIDTH <= widthPx) {
ctx.fillText(
LOADING_TEXT,
leftPx + widthPx / 2 - LOADING_TEXT_WIDTH / 2,
heightPx / 2);
}
ctx.textBaseline = oldBaseline;
}
/**
* Checker board everything between [startPx, endPx] except [leftPx, rightPx].
*/
export function checkerboardExcept(
ctx: CanvasRenderingContext2D,
heightPx: number,
startPx: number,
endPx: number,
leftPx: number,
rightPx: number): void {
// [leftPx, rightPx] doesn't overlap [startPx, endPx] at all:
if (rightPx <= startPx || leftPx >= endPx) {
checkerboard(ctx, heightPx, startPx, endPx);
return;
}
// Checkerboard [startPx, leftPx]:
if (leftPx > startPx) {
checkerboard(ctx, heightPx, startPx, leftPx);
}
// Checkerboard [rightPx, endPx]:
if (rightPx < endPx) {
checkerboard(ctx, heightPx, rightPx, endPx);
}
}