snapshot: a whole new approach to panning
Basic idea: If the goal is for the cursor to be on the viewport, focus the code on ensuring that constraint by construction. Motivation: The downstream driver.love fork still has persistent bugs. And I'm seeing some inconclusive signs that edit.lua might be failing to change screen_top some of the time when it needs to. But this only happens in driver.love, never in lines.love. So the null hypothesis is that there's some subtle assumption in lines.love that we're violating when rendering it on a surface. What do you do with such subtleties? It might actually be counterproductive to fix them at source. You end up with complexity upstream that won't actually matter there if it breaks. Which is a recipe for it to break silently and far away from the downstream fork that might actually care about it. Or it might confuse people in future who don't care about the downstream forks, just lines.love. Maybe it makes sense to modify edit.lua here and take the hit on all possible future merge conflicts. But considering the cost of tracking this down, it seems simplest to: a) come up with the constraint I care about, and b) modify outside edit.lua, either what it sees or its results, to preserve the new constraint. Long ago I used to have this assertion in pensieve.love that the cursor must be within the viewport, but I ended up taking it out because it kept breaking for me when I was trying to do real work. It seems clear that there are possible assertions that are useful and yet counterproductive. If you can't keep it out of the product in the course of testing, then it annoys users where ignoring it would be a more graceful experience. Even when the user is just yourself! So it turns out this is not a problem only for large teams of extrinsically motivated people who don't eat their own dog food. No, for some things you have to fix the problem by construction, not just verify it with an assertion. This plan isn't fully working yet in this commit. I've only fixed cases for down-arrow. I need to address up arrow, and there might also be changes for left/right arrows. Hmm, I'm going to try to follow the implementation of bring_cursor_of_cursor_node_in_view() in pensieve.love. In the process of doing this I also noticed a bug with page-up/down. It already existed, but this approach has made it more obvious.
This commit is contained in:
Kartik K. Agaram
parent
4eee6a1ac2
commit
1031f47496
4
0019-B
4
0019-B
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@ -1,4 +1,4 @@
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B = function(skip_updating_screen_top_for)
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B = function()
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-- recompute various aspects based on the current viewport settings
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for _,obj in ipairs(Surface) do
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if obj.type == 'line' then
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@ -16,7 +16,7 @@ B = function(skip_updating_screen_top_for)
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obj.zdata = love.math.newBezierCurve(zdata):render()
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elseif obj.type == 'text' then
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if obj.w then
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update_editor_box(obj, skip_updating_screen_top_for)
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update_editor_box(obj)
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else
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obj.text = love.graphics.newText(love.graphics.getFont(), obj.data)
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end
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@ -1,4 +1,4 @@
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compute_layout = function(node, x,y, nodes_to_render, skip_updating_screen_top_for)
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compute_layout = function(node, x,y, nodes_to_render)
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-- append to nodes_to_render flattened instructions to render a hierarchy of nodes
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-- return x,y rendered until (surface coordinates)
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if node.type == 'text' then
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@ -31,7 +31,7 @@ compute_layout = function(node, x,y, nodes_to_render, skip_updating_screen_top_f
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if node.editor == nil then
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initialize_editor(node)
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else
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update_editor_box(node, skip_updating_screen_top_for)
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update_editor_box(node)
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end
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node.h = box_height(node)
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table.insert(nodes_to_render, node)
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@ -59,7 +59,7 @@ compute_layout = function(node, x,y, nodes_to_render, skip_updating_screen_top_f
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if not child.width then
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child.width = node.width -- HACK: should we set child.w or child.width? Neither is quite satisfactory.
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end
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subx,suby = compute_layout(child, x,suby, nodes_to_render, skip_updating_screen_top_for)
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subx,suby = compute_layout(child, x,suby, nodes_to_render)
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if w < child.w then
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w = child.w
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end
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@ -87,7 +87,7 @@ compute_layout = function(node, x,y, nodes_to_render, skip_updating_screen_top_f
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subx = subx+child.margin
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w = w+child.margin
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end
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subx,suby = compute_layout(child, subx,y, nodes_to_render, skip_updating_screen_top_for)
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subx,suby = compute_layout(child, subx,y, nodes_to_render)
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w = w + child.w
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if h < child.h then
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h = child.h
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@ -17,27 +17,10 @@ on.keychord_press = function(chord, key)
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elseif chord == 'C-z' then
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dump_state()
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elseif Cursor_node and Cursor_node.editor.cursor_x then
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local old_top = {line=Cursor_node.editor.screen_top1.line, pos=Cursor_node.editor.screen_top1.pos}
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print('cursor before', Cursor_node.editor.cursor1.line, Cursor_node.editor.cursor1.pos)
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edit.keychord_press(Cursor_node.editor, chord, key)
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--? print('edit', old_top.line, '=>', Cursor_node.editor.screen_top1.line)
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if not eq(Cursor_node.editor.screen_top1, old_top) then
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--? print('modifying Viewport', Viewport.y, 'based on', Cursor_node.y, Cursor_node.editor.screen_top1.line, Cursor_node.editor.line_height)
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Viewport.y = Cursor_node.y + y_of_schema1(Cursor_node.editor, Cursor_node.editor.screen_top1)/Viewport.zoom
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--? print('modified Viewport', Viewport.y)
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-- Most of the time, we update the screen_top of nodes from Viewport.y.
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-- But here we went the other way.
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-- It's very important to avoid creating a recurrence, to avoid running
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-- both sides of this feedback loop in a single frame. These apps are
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-- not very numerically precise (e.g. we force text lines to start at
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-- integer pixels regardless of zoom, because that keeps text crisp),
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-- and the computations of Viewport.y and node.top will almost certainly
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-- not converge. The resulting bugs are extremely difficult to chase
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-- down.
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-- The optional skip_updating_screen_top_for arg ensures we don't run
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-- the other side of the feedback loop.
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A(--[[skip updating screen_top for]] Cursor_node)
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return
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end
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print('cursor after', Cursor_node.editor.cursor1.line, Cursor_node.editor.cursor1.pos)
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pan_viewport_to_contain_cursor(Cursor_node)
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A()
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else
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if chord == 'up' then
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8
0028-A
8
0028-A
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@ -1,4 +1,4 @@
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A = function(skip_updating_screen_top_for)
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A = function()
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love.graphics.setFont(love.graphics.newFont(scale(20))) -- editor objects implicitly depend on current font
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-- translate Page and Page2 to Surface
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Surface = {}
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@ -9,9 +9,9 @@ A = function(skip_updating_screen_top_for)
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red = not red
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end
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end
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compute_layout(Page, Page.x,Page.y, Surface, skip_updating_screen_top_for)
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compute_layout(Page2, Page2.x,Page2.y, Surface, skip_updating_screen_top_for)
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compute_layout(Page, Page.x,Page.y, Surface)
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compute_layout(Page2, Page2.x,Page2.y, Surface)
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-- continue the pipeline
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B(skip_updating_screen_top_for)
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B()
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-- TODO: ugly that we're manipulating editor objects twice
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end
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@ -1,29 +1,16 @@
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update_editor_box = function(node, skip_updating_screen_top_for)
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update_editor_box = function(node, skip_updating)
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if node.editor == nil then return end
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if node == skip_updating then return end
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edit.update_font_settings(node.editor, scale(20))
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node.editor.left = math.floor(vx(node.x))
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node.editor.right = math.ceil(vx(node.x+node.w))
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node.editor.width = node.editor.right - node.editor.left
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Text.redraw_all(node.editor)
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--? print('update', node.y, Viewport.y, 'spx', node.editor.screen_top1.line, node.editor.top, 'vpx')
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if node.y > Viewport.y then
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if node ~= skip_updating_screen_top_for then
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--? print('modifying screen_top to 1')
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node.editor.screen_top1.line = 1
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node.editor.screen_top1.pos = 1
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end
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node.editor.screen_top1.line = 1
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node.editor.screen_top1.pos = 1
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node.editor.top = vy(node.y)
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else
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--? print('<=', node, skip_updating_screen_top_for)
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if node ~= skip_updating_screen_top_for then
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node.editor.screen_top1, node.editor.top = schema1_of_y(node.editor, scale(Viewport.y-node.y))
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print('modified screen_top to', node.editor.screen_top1.line, 'at', node.editor.top, 'vpx')
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else
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-- adjust editor to start rendering near top of viewport
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--? print(Viewport.y)
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node.editor.top = Viewport.y%node.editor.line_height
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if node.editor.top > 0 then node.editor.top = node.editor.top - node.editor.line_height end
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--? print('top', node.editor.top)
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end
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node.editor.screen_top1, node.editor.top = schema1_of_y(node.editor, scale(Viewport.y-node.y))
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end
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end
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@ -0,0 +1,31 @@
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function pan_viewport_to_contain_cursor(node)
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print('viewport', Viewport.y)
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local safety_margin = 2*node.editor.line_height
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print('safety margin', screen_top_y, 'dvpx')
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print('node', node.y)
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local cursor_y = y_of_schema1(node.editor, node.editor.cursor1)
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print('cursor', cursor_y, 'dvpx')
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if Viewport.y < node.y then
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-- node starts within Viewport
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print('node starts within viewport')
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local max_cursor_y = App.screen.height - scale(node.y - Viewport.y) - safety_margin
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if cursor_y > max_cursor_y then
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-- set Viewport.y so cursor_y == max_cursor_y
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-- equation: cursor_y == App.screen.height - (node.y - Viewport.y)*Viewport.zoom - safety_margin
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-- solve for Viewport.y
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Viewport.y = node.y - (App.screen.height - cursor_y - safety_margin)/Viewport.zoom
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print('adjusting Viewport to', Viewport.y)
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end
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else
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-- node extends above Viewport
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print('node extends above viewport')
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local screen_top_y = y_of_schema1(node.editor, node.editor.screen_top1)
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print('screen top', screen_top_y, 'dvpx')
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local min_screen_top_y = cursor_y + safety_margin - App.screen.height
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if screen_top_y < min_screen_top_y then
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screen_top_y = min_screen_top_y
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Viewport.y = node.y + screen_top_y/Viewport.zoom
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print('adjusting Viewport to', Viewport.y)
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end
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end
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end
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