https://khieu.ch/Building a pixel-faithful Office renderer for the web, and writing down what Office really does.en https://khieu.ch/writing/against-the-others/https://khieu.ch/writing/against-the-others/Sat, 07 Nov 2026 12:00:00 GMTComparing renderers only means something when they draw with the same fonts. Here's what happened when I gave them all exactly the same files. https://khieu.ch/writing/the-spec-is-rotated/https://khieu.ch/writing/the-spec-is-rotated/Sat, 07 Nov 2026 12:00:00 GMTOffice's specification lists exactly where its 3-D lights point. Draw them as written and the highlights land in the wrong place. Turn them a quarter turn and everything matches. https://khieu.ch/writing/thousands-of-files-one-score/https://khieu.ch/writing/thousands-of-files-one-score/Fri, 06 Nov 2026 12:00:00 GMTHow I measure whether the renderer really looks like Office. Office's own PDFs as the reference, a Windows PC doing the exports, and a score for every file. Tonight it's at 89.3. https://khieu.ch/writing/the-pdf-is-the-page/https://khieu.ch/writing/the-pdf-is-the-page/Fri, 06 Nov 2026 12:00:00 GMTFor months every PDF in the product came from a second program. This week the PDF finally prints what the screen draws. https://khieu.ch/writing/the-camera-behind-3d-pies/https://khieu.ch/writing/the-camera-behind-3d-pies/Wed, 04 Nov 2026 12:00:00 GMTOffice never says how it draws a 3-D pie. But its PDFs contain the picture, and a picture of a cylinder gives away the camera that took it. https://khieu.ch/writing/smartart-fits-text-by-guessing/https://khieu.ch/writing/smartart-fits-text-by-guessing/Tue, 03 Nov 2026 12:00:00 GMTSmartArt doesn't calculate the size that fits. It searches for it, halving the gap each step, and stops when it's close enough. That leaves fingerprints. https://khieu.ch/writing/powerpoint-kerns-with-an-old-table/https://khieu.ch/writing/powerpoint-kerns-with-an-old-table/Mon, 02 Nov 2026 12:00:00 GMTGetting SmartArt text to fit like it does in PowerPoint came down to one rule I never found written anywhere. Kerning starts at 12 pt, and it uses the font's old kern table. https://khieu.ch/writing/a-codec-for-one-image-format/https://khieu.ch/writing/a-codec-for-one-image-format/Wed, 28 Oct 2026 12:00:00 GMTPowerPoint quietly keeps the original of every edited picture in a format almost nothing reads. So yesterday I finished a decoder and an encoder in plain JavaScript. https://khieu.ch/writing/opening-everything-in-a-tab/https://khieu.ch/writing/opening-everything-in-a-tab/Wed, 14 Oct 2026 12:00:00 GMTOnce slides worked without a server, I got curious about what else a tab can open by itself. Old Word files, iPhone photos, mail, ebooks, archives. https://khieu.ch/writing/fonts-you-dont-have/https://khieu.ch/writing/fonts-you-dont-have/Sat, 10 Oct 2026 12:00:00 GMTMost Office documents ask for fonts a browser doesn't have and can't legally ship. This week I found a way to stand in for them without the text reflowing. https://khieu.ch/writing/a-pdf-inside-a-picture/https://khieu.ch/writing/a-pdf-inside-a-picture/Sun, 27 Sep 2026 12:00:00 GMTPasted charts and logos in Office files are often EMF, a Windows format no browser can draw. The ones from Word for Mac carry a surprise. https://khieu.ch/writing/powerpoint-as-the-answer-key/https://khieu.ch/writing/powerpoint-as-the-answer-key/Wed, 26 Aug 2026 12:00:00 GMTWith LibreOffice out of the picture I need a new reference. PowerPoint's own PDF export states almost everything it does, if you read it closely. https://khieu.ch/writing/libreoffice-in-the-browser/https://khieu.ch/writing/libreoffice-in-the-browser/Tue, 25 Aug 2026 12:00:00 GMTYesterday a full office suite booted in a browser tab. A few hours later my own JavaScript drew the same slides, with zero differences, 275 times faster. https://khieu.ch/writing/a-pdf-that-looked-right/https://khieu.ch/writing/a-pdf-that-looked-right/Sun, 23 Aug 2026 12:00:00 GMTMy fundraising tool for non-profits keeps producing PDFs that don't match the slides. Tomorrow I'm trying something different.