Show filtered lists and their shared focus

A list may now be filtered (each t in tasks where !t.done), and several
filtered lists over one list share one focus: the focus view names an
item, so Vega asks Pure which row shows it and highlights it only in the
list that holds it; the other lists have no focus (null in the web
surface's JSON, and the spoken surface names the item where it is). A
click or point on a row points at the item that row shows, and the wheel
on a list without the focus focuses the row under it. Pure's rows now
take a mutable app.

examples/today.aup shows what is open and what is done; its CLI output
matches a model over random adds, moves, toggles and points into either
list, and the web surface leaves the other list without a focus.

5 files changed, 38 insertions, 17 deletions

diff --git a/src/draw.c b/src/draw.c
index 738c2db..31188c7 100644
--- a/src/draw.c
+++ b/src/draw.c
@@ -138,6 +138,7 @@ static void say_focus(FILE *out, PureApp *app, const VegaPart *part) {
     size_t length, rows = vega_rows(app, part);
     if (!rows) { fprintf(out, "%s is empty.\n", m->view_names[part->view]); return; }
     size_t focus = vega_focus(app, part);
+    if (focus >= rows) { fprintf(out, "%s: none of %zu focused.\n", m->view_names[part->view], rows); return; }
     fprintf(out, "Item %zu of %zu: ", focus + 1, rows);
     VegaTone tone = vega_tone(app, part, focus);
     if (tone >= VEGA_ACCENT) fprintf(out, "%s, ", tone_names[tone]);
@@ -164,8 +165,15 @@ void vega_say(FILE *out, PureApp *app, const VegaScreen *screen, bool all) {
     char text[VEGA_TEXT];
     size_t length;
     if (!all) {
-        for (unsigned i = 0; i < screen->count; ++i)
-            if (screen->parts[i].kind != VEGA_FIELD) { say_focus(out, app, &screen->parts[i]); return; }
+        /* The focused item where a list shows it, else the first list. */
+        const VegaPart *first = NULL;
+        for (unsigned i = 0; i < screen->count; ++i) {
+            const VegaPart *part = &screen->parts[i];
+            if (part->kind == VEGA_FIELD) continue;
+            if (!first) first = part;
+            if (vega_focus(app, part) < vega_rows(app, part)) { say_focus(out, app, part); return; }
+        }
+        if (first) say_focus(out, app, first);
         return;
     }
     if (screen->title >= 0 && vega_text(app, (uint32_t)screen->title, 0, text, &length)) {
diff --git a/src/main.c b/src/main.c
index 46b672f..b9ea91e 100644
--- a/src/main.c
+++ b/src/main.c
@@ -95,8 +95,10 @@ static bool mouse(unsigned button, unsigned line) {
     const VegaPart *part = &screen.parts[index];
     if (button == 64 || button == 65) {
         size_t focus = vega_focus(&app, part), rows = vega_rows(&app, part);
-        if (button == 64 ? !focus : focus + 1 >= rows) return false;
-        item = button == 64 ? focus - 1 : focus + 1;
+        if (focus < rows) { /* else the wheel focuses the row under it */
+            if (button == 64 ? !focus : focus + 1 >= rows) return false;
+            item = button == 64 ? focus - 1 : focus + 1;
+        }
     } else if (button) return false;
     return vega_point(&app, part, item);
 }
diff --git a/src/screen.c b/src/screen.c
index bb50de1..26b9fb0 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -146,20 +146,23 @@ bool vega_number(PureApp *app, uint32_t view, size_t row, double *out) {
     return app->module->view_table[view] ? pure_app_cell(app, view, row, out) : pure_app_view(app, view, out);
 }
 
-size_t vega_rows(const PureApp *app, const VegaPart *part) {
+size_t vega_rows(PureApp *app, const VegaPart *part) {
     return part->kind == VEGA_FIELD ? 0 : pure_app_rows(app, part->view);
 }
 
 size_t vega_focus(PureApp *app, const VegaPart *part) {
-    size_t rows = vega_rows(app, part);
+    size_t rows = vega_rows(app, part), row;
     double focus;
     if (part->focus < 0 || !rows || !vega_number(app, (uint32_t)part->focus, 0, &focus) || !(focus >= 0)) return 0;
-    return focus >= (double)(rows - 1) ? rows - 1 : (size_t)focus;
+    bool filtered = app->module->view_code[part->view].length > 0;
+    size_t item = focus < (double)SIZE_MAX ? (size_t)focus : SIZE_MAX;
+    if (pure_app_item_row(app, part->view, item, &row)) return row;
+    return filtered ? VEGA_NO_ROW : rows - 1;
 }
 
 size_t vega_scroll(size_t first, size_t focus, size_t visible, size_t rows) {
-    if (focus < first) first = focus;
-    if (visible && focus >= first + visible) first = focus - visible + 1;
+    if (focus < rows && focus < first) first = focus;
+    if (focus < rows && visible && focus >= first + visible) first = focus - visible + 1;
     if (first + visible > rows) first = rows > visible ? rows - visible : 0;
     return first;
 }
@@ -184,7 +187,9 @@ bool vega_commit(PureApp *app, const VegaScreen *screen, const char *text, size_
 }
 
 bool vega_point(PureApp *app, const VegaPart *part, size_t row) {
-    return part->pointer >= 0 && pure_app_point(app, (uint32_t)part->pointer, row) == PURE_OK;
+    size_t item; /* a filtered list's row shows some item of the list */
+    return part->pointer >= 0 && pure_app_row_item(app, part->view, row, &item) &&
+           pure_app_point(app, (uint32_t)part->pointer, item) == PURE_OK;
 }
 
 VegaTone vega_tone(PureApp *app, const VegaPart *part, size_t row) {
diff --git a/src/vega.h b/src/vega.h
index 98ed410..59a663e 100644
--- a/src/vega.h
+++ b/src/vega.h
@@ -45,14 +45,18 @@ unsigned vega_check(const PureModule *, void (*report)(void *, const char *name,
  * shortest form. false when it has no value (for example a missing item). */
 bool vega_text(PureApp *, uint32_t view, size_t row, char out[VEGA_TEXT], size_t *length);
 bool vega_number(PureApp *, uint32_t view, size_t row, double *out);
-size_t vega_rows(const PureApp *, const VegaPart *);
-/* The focused row, clamped to the rows; 0 without a focus view. */
+size_t vega_rows(PureApp *, const VegaPart *);
+/* The row of the focused item: the focus view names an item (an index's
+ * position), shown on the row that holds it; VEGA_NO_ROW when a filtered
+ * list leaves that item out. Clamped to the rows without a filter; 0
+ * without a focus view. */
+#define VEGA_NO_ROW SIZE_MAX
 size_t vega_focus(PureApp *, const VegaPart *);
 /* Focus a row, as a user pointing at it (a click); false when the part's
  * focus is not a plain index position or the row is not there. */
 bool vega_point(PureApp *, const VegaPart *, size_t row);
 /* The first row to show of `rows` when `visible` fit: the least scrolling
- * from first that keeps the focused row in view. */
+ * from first that keeps the focused row in view (any, without one). */
 size_t vega_scroll(size_t first, size_t focus, size_t visible, size_t rows);
 /* The key input answering a key name (Pure's names, as KeyboardEvent.code
  * spells them), or -1; press sends its press and release. */
diff --git a/src/web.c b/src/web.c
index 78da0ab..149e888 100644
--- a/src/web.c
+++ b/src/web.c
@@ -123,8 +123,10 @@ static void screen_json(Buffer *b, PureApp *app, const VegaScreen *screen, size_
         puts_(b, comma ? ",{\"part\":" : "{\"part\":");
         putf(b, "%u,\"name\":", i);
         json_name(b, m->view_names[part->view]);
-        putf(b, ",\"kind\":\"%s\",\"rows\":%zu,\"focus\":%zu,\"first\":%zu,\"pointable\":%s,\"columns\":[",
-             part->kind == VEGA_LIST ? "list" : "table", rows, rows ? focus : 0, first, part->pointer >= 0 ? "true" : "false");
+        putf(b, ",\"kind\":\"%s\",\"rows\":%zu,\"focus\":", part->kind == VEGA_LIST ? "list" : "table", rows);
+        if (focus < rows) putf(b, "%zu", focus);
+        else puts_(b, "null");
+        putf(b, ",\"first\":%zu,\"pointable\":%s,\"columns\":[", first, part->pointer >= 0 ? "true" : "false");
         if (part->kind == VEGA_TABLE)
             for (unsigned c = 0; c < part->column_count; ++c) {
                 if (c) puts_(b, ",");
@@ -224,12 +226,12 @@ static const char *const page_parts[] = {
 "el('span',{className:'label',textContent:it.label?\?''}),it.detail?el('span',{className:'detail',textContent:it.detail}):null,"
 "it.badge?el('span',{className:'badge',textContent:it.badge}):null);item.setAttribute('role','option');"
 "item.setAttribute('aria-selected',it.row===p.focus);list.append(item)}"
-"list.onwheel=e=>{e.preventDefault();pick(Math.max(0,Math.min(p.rows-1,p.focus+Math.sign(e.deltaY))))};"
+"list.onwheel=e=>{e.preventDefault();pick(Math.max(0,Math.min(p.rows-1,(p.focus?\?-1)+Math.sign(e.deltaY))))};"
 "return el('section',{},head,list)}"
 "const table=el('table',{},el('thead',{},el('tr',{},...p.columns.map(c=>el('th',{textContent:c})))));"
 "const body=el('tbody');for(const it of p.items){const tr=el('tr',{className:it.tone,onclick:()=>pick(it.row)},"
 "...it.cells.map(c=>el('td',{textContent:c?\?'-'})));tr.setAttribute('aria-selected',it.row===p.focus);body.append(tr)}"
-"table.append(body);table.onwheel=e=>{e.preventDefault();pick(Math.max(0,Math.min(p.rows-1,p.focus+Math.sign(e.deltaY))))};"
+"table.append(body);table.onwheel=e=>{e.preventDefault();pick(Math.max(0,Math.min(p.rows-1,(p.focus?\?-1)+Math.sign(e.deltaY))))};"
 "return el('section',{},head,table)}));"
 "$('prompt').hidden=!s.prompt;if(s.prompt)$('entry').placeholder=s.prompt;"
 "const symbols={ArrowUp:'\u2191',ArrowDown:'\u2193',ArrowLeft:'\u2190',ArrowRight:'\u2192',Backspace:'Bksp',"