\n Observe that we paint all 100 lines in our paint handler, even though most of them\n aren’t visible. This is a problem if there are a large number of items, or if painting\n an item is time-consuming.\n <\/p>\n
\n So instead, we optimize our paint cycle so as to paint only the elements which intersect\n the paint rectangle.\n <\/p>\n
void\nPaintSimpleContent(HWND hwnd, PAINTSTRUCT *pps)\n{\n HFONT hfPrev = SelectFont(pps->hdc, g_hfList); \/* Use the right font *\/\n int iMin = max(pps->rcPaint.top \/ g_cyLine, 0);\n int iMax = min((pps->rcPaint.bottom + g_cyLine - 1) \/ g_cyLine, g_cItems);\n for (int i = iMin; i < iMax; i++) {\n char szLine[256];\n int cch = wsprintf(szLine, \"This is line %d\", i);\n TextOut(pps->hdc, 0, i * g_cyLine, szLine, cch);\n }\n SelectFont(pps->hdc, hfPrev);\n}\n<\/pre>\n\n Exercise: Explain the formulas for iMin<\/i> and iMax<\/i>. Explain why the seemingly\n equivalent formula\n <\/p>\n int iMax = min((pps->rcPaint.bottom - 1) \/ g_cyLine + 1, g_cItems);\n<\/pre>\n\n is wrong. Then explain why it doesn’t really matter too much.\n <\/p>\n","protected":false},"excerpt":{"rendered":"
Observe that we paint all 100 lines in our paint handler, even though most of them aren’t visible. This is a problem if there are a large number of items, or if painting an item is time-consuming. So instead, we optimize our paint cycle so as to paint only the elements which intersect the paint […]<\/p>\n","protected":false},"author":1069,"featured_media":111744,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[25],"class_list":["post-43033","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-oldnewthing","tag-code"],"acf":[],"blog_post_summary":"
Observe that we paint all 100 lines in our paint handler, even though most of them aren’t visible. This is a problem if there are a large number of items, or if painting an item is time-consuming. So instead, we optimize our paint cycle so as to paint only the elements which intersect the paint […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/43033","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/users\/1069"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/comments?post=43033"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/43033\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/media\/111744"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/media?parent=43033"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/categories?post=43033"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/tags?post=43033"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}