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broadway: Optionally support data: uris instead of blobs

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This is nice when you want to make a "screenshot" by using save-as.
Its not going to perform as well though, so you have to enable it
by adding ?datauri to the url
This commit is contained in:
Alexander Larsson 2019-03-29 13:18:17 +01:00
parent 4e7eccbb49
commit 5bc8f8826f
1 changed files with 69 additions and 3 deletions
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72
gdk/broadway/broadway.js
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@ -93,6 +93,63 @@ const GDK_HYPER_MASK = 1 << 27;
const GDK_META_MASK = 1 << 28;
const GDK_RELEASE_MASK = 1 << 30;
var useDataUrls = window.location.search.includes("datauri");
/* This base64code is based on https://github.com/beatgammit/base64-js/blob/master/index.js which is MIT licensed */
var b64_lookup = [];
var base64_code = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
for (var i = 0, len = base64_code.length; i < len; ++i) {
b64_lookup[i] = base64_code[i];
}
function tripletToBase64 (num) {
return b64_lookup[num >> 18 & 0x3F] +
b64_lookup[num >> 12 & 0x3F] +
b64_lookup[num >> 6 & 0x3F] +
b64_lookup[num & 0x3F];
}
function encodeBase64Chunk (uint8, start, end) {
var tmp;
var output = [];
for (var i = start; i < end; i += 3) {
tmp =
((uint8[i] << 16) & 0xFF0000) +
((uint8[i + 1] << 8) & 0xFF00) +
(uint8[i + 2] & 0xFF);
output.push(tripletToBase64(tmp));
}
return output.join('');
}
function bytesToDataUri(uint8) {
var tmp;
var len = uint8.length;
var extraBytes = len % 3; // if we have 1 byte left, pad 2 bytes
var parts = [];
var maxChunkLength = 16383; // must be multiple of 3
parts.push("data:image/png;base64,");
// go through the array every three bytes, we'll deal with trailing stuff later
for (var i = 0, len2 = len - extraBytes; i < len2; i += maxChunkLength) {
parts.push(encodeBase64Chunk(uint8, i, (i + maxChunkLength) > len2 ? len2 : (i + maxChunkLength)));
}
// pad the end with zeros, but make sure to not forget the extra bytes
if (extraBytes === 1) {
tmp = uint8[len - 1];
parts.push(b64_lookup[tmp >> 2] + b64_lookup[(tmp << 4) & 0x3F] + '==');
} else if (extraBytes === 2) {
tmp = (uint8[len - 2] << 8) + uint8[len - 1];
parts.push(b64_lookup[tmp >> 10] + b64_lookup[(tmp >> 4) & 0x3F] + b64_lookup[(tmp << 2) & 0x3F] + '=');
}
return parts.join('');
}
/* Helper functions for debugging */
var logDiv = null;
function log(str) {
@ -202,8 +259,15 @@ function getButtonMask (button) {
}
function Texture(id, data) {
var blob = new Blob([data],{type: "image/png"});
this.url = window.URL.createObjectURL(blob);
var url;
if (useDataUrls) {
url = bytesToDataUri(data);
} else {
var blob = new Blob([data],{type: "image/png"});
url = window.URL.createObjectURL(blob);
}
this.url = url;
this.refcount = 1;
this.id = id;
@ -221,7 +285,9 @@ Texture.prototype.ref = function() {
Texture.prototype.unref = function() {
this.refcount -= 1;
if (this.refcount == 0) {
window.URL.revokeObjectURL(this.url);
if (this.url.startsWith("blob")) {
window.URL.revokeObjectURL(this.url);
}
delete textures[this.id];
}
}