From 2b07553aa127f9ab0783de754a68b0b3bca95de6 Mon Sep 17 00:00:00 2001 From: Simon Forman Date: Sun, 26 Feb 2023 15:24:40 -0800 Subject: [PATCH] Draw chars when you click. Pick a letter at random. I wasn't checking that the destination values were not less than zero, which let you click at the top/left edges of the screen and therefore the carefree_alpha_blend_blit() would try to write to areas outside the framebuffer. I started to see "zalgol" pixels in the letters, so I'm guessing the pixel data is getting stored just above the framebuffer, which makes sense (because that's the order they appear in the source code and this is a simple system!) When you click at the top of the screen it was writing pixels in the font data, eh? Then when you click elsewhere on the screen you get extra pixels with your letterforms and it looks like Unicode Lovecraft puns. --- implementations/uvm-ncc/xerblin.c | 27 ++++++++++++++++++++------- 1 file changed, 20 insertions(+), 7 deletions(-) diff --git a/implementations/uvm-ncc/xerblin.c b/implementations/uvm-ncc/xerblin.c index d3a3cbe..db95a61 100644 --- a/implementations/uvm-ncc/xerblin.c +++ b/implementations/uvm-ncc/xerblin.c @@ -13,20 +13,23 @@ u32 frame_buffer[393216]; int wid; // Window ID. +// Current mouse pointer position +size_t pos_x = 200; +size_t pos_y = 200; + void draw_char(u8 ch, u64 dest_x, u64 dest_y) { // Check the inputs. - // Trust that the type "u-" means we don't have to check lower bounds? - if (ch > font_Inconsolata_22_number_of_characters) { + if (ch < 0 || ch > font_Inconsolata_22_number_of_characters) { // No error message or anything, just decline to draw. return; } - if (dest_x >= (FRAME_WIDTH - font_Inconsolata_22_width)) { + if (dest_x < 0 || dest_x >= (FRAME_WIDTH - font_Inconsolata_22_width)) { return; } - if (dest_y >= (FRAME_HEIGHT - font_Inconsolata_22_height)) { + if (dest_y < 0 || dest_y >= (FRAME_HEIGHT - font_Inconsolata_22_height)) { return; } carefree_alpha_blend_blit( @@ -49,14 +52,23 @@ draw_char(u8 ch, u64 dest_x, u64 dest_y) void -mousedown(u64 window_id, u64 new_x, u64 new_y) +mousedown(u64 window_id, u8 btn_id) { - u32* pix_ptr = frame_buffer + FRAME_WIDTH * new_y + new_x; - *pix_ptr = GREEN; + u8 ch = rand() % font_Inconsolata_22_number_of_characters; + draw_char(ch, pos_x - font_Inconsolata_22_width, pos_y - font_Inconsolata_22_height); window_draw_frame(window_id, frame_buffer); } +void +mousemove(u64 window_id, u64 new_x, u64 new_y) +{ + // Update the mouse position + pos_x = new_x; + pos_y = new_y; +} + + void main() { @@ -73,5 +85,6 @@ main() window_draw_frame(wid, frame_buffer); //window_on_keydown(wid, keydown); window_on_mousedown(wid, mousedown); + window_on_mousemove(wid, mousemove); enable_event_loop(); }