{"id":43,"date":"2017-06-26T13:37:02","date_gmt":"2017-06-26T13:37:02","guid":{"rendered":"https:\/\/blogs.scummvm.org\/joefish-gsoc\/?p=43"},"modified":"2022-05-21T14:09:22","modified_gmt":"2022-05-21T14:09:22","slug":"drawing-the-cursor","status":"publish","type":"post","link":"https:\/\/blogs.scummvm.org\/joefish-gsoc\/2017\/06\/26\/drawing-the-cursor\/","title":{"rendered":"Drawing the Cursor"},"content":{"rendered":"

\"\"<\/a> Seems like our Chef Horst Hummel got impatient and sliced the hourglass cleanly in half..<\/p>\n

The 16×16 cursor image is stored as a bitmap like the newspaper images I described in my previous post on graphics and animation in Supernova<\/a>. The black outline and red filling are rendered seperately, both taking 32 bytes<\/a>.<\/p>\n

I skimmed through my code and could not find a shift that possibly corrupted the cursor data. But how to fix it? Well, it seems the image is split right at 8 pixels and since they are represented by one byte we could just do a wordRoll that swaps its bytes like wapped = (i >> 8) | (i << 8)<\/code>.<\/p>\n

The disassembly shows the critical part for drawing the black outline<\/p>\n

\n
next_line:<\/span>\r\n<\/a>          lodsw<\/span>\r\n<\/a>          mov cx,dx<\/span>\r\n<\/a>\r\n<\/a>next_pixel:<\/span>\r\n<\/a>          shl ax,1<\/span>\r\n<\/a>          jc skip1<\/span>\r\n<\/a>          mov byte es:[di],0<\/span>\r\n<\/a>skip1:<\/span>\r\n<\/a>          inc di<\/span>\r\n<\/a>          loop next_pixel<\/span>\r\n<\/a>\r\n<\/a>          add di,320<\/span>\r\n<\/a>          sub di,dx<\/span>\r\n<\/a>          dec bh<\/span>\r\n<\/a>          jnz next_line\r\n<\/span><\/pre>\n<\/blockquote>\n
lodsw<\/b>… The first endianess bug in this project that I got stuck on…
\nAt least now it’s working and I can keep going with more important stuff like actually making it playable and hopefully won’t get distracted by those small things again…<\/p>\n
\"\"<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
Seems like our Chef Horst Hummel got impatient and sliced the hourglass cleanly in half.. The 16×16 cursor image is stored as a bitmap like the newspaper images I described in my previous post on graphics and animation in Supernova. The black outline and red filling are rendered seperately, both taking 32 bytes. I skimmed […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-43","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/blogs.scummvm.org\/joefish-gsoc\/wp-json\/wp\/v2\/posts\/43","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.scummvm.org\/joefish-gsoc\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.scummvm.org\/joefish-gsoc\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.scummvm.org\/joefish-gsoc\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.scummvm.org\/joefish-gsoc\/wp-json\/wp\/v2\/comments?post=43"}],"version-history":[{"count":3,"href":"https:\/\/blogs.scummvm.org\/joefish-gsoc\/wp-json\/wp\/v2\/posts\/43\/revisions"}],"predecessor-version":[{"id":49,"href":"https:\/\/blogs.scummvm.org\/joefish-gsoc\/wp-json\/wp\/v2\/posts\/43\/revisions\/49"}],"wp:attachment":[{"href":"https:\/\/blogs.scummvm.org\/joefish-gsoc\/wp-json\/wp\/v2\/media?parent=43"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.scummvm.org\/joefish-gsoc\/wp-json\/wp\/v2\/categories?post=43"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.scummvm.org\/joefish-gsoc\/wp-json\/wp\/v2\/tags?post=43"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}