trezor.ui.text: add work break and configurable new_lines

Now it is possible to combine multiple font styles per line,
a nd to manually control line breaks with trezor.ui.text.BR.

src/trezor/ui/text.py

@@ -4,36 +4,110 @@ from trezor import ui
 TEXT_HEADER_HEIGHT = const(48)
 TEXT_LINE_HEIGHT = const(26)
 TEXT_MARGIN_LEFT = const(14)
+TEXT_MAX_LINES = const(4)
+
+BR = const(-1)
+
+
+def render_words(words: list, new_lines: bool, max_lines: int) -> None:
+    # initial rendering state
+    font = ui.NORMAL
+    fg = ui.FG
+    bg = ui.BG
+    offset_x = TEXT_MARGIN_LEFT
+    offset_y = TEXT_HEADER_HEIGHT + TEXT_LINE_HEIGHT
+    OFFSET_X_MAX = ui.WIDTH
+    OFFSET_Y_MAX = TEXT_HEADER_HEIGHT + TEXT_LINE_HEIGHT * max_lines
+
+    # sizes of common glyphs
+    SPACE = ui.display.text_width(' ', font)
+    DASH = ui.display.text_width('-', ui.BOLD)
+    ELLIPSIS = ui.display.text_width('...', ui.BOLD)
+
+    for word in words:
+        if isinstance(word, int):
+            if word == BR:
+                # line break
+                if not offset_y < OFFSET_Y_MAX:
+                    ui.display.text(offset_x, offset_y, '...', ui.BOLD, ui.GREY, bg)
+                    return
+                offset_x = TEXT_MARGIN_LEFT
+                offset_y += TEXT_LINE_HEIGHT
+            elif word == ui.NORMAL or word == ui.BOLD or word == ui.MONO:
+                # change of font style
+                font = word
+            else:
+                # change of foreground color
+                fg = word
+            continue
+
+        width = ui.display.text_width(word, font)
+
+        while offset_x + width + SPACE + ELLIPSIS > OFFSET_X_MAX:
+            space_for_another_line = offset_y < OFFSET_Y_MAX
+            word_fits_in_one_line = width < (OFFSET_X_MAX - TEXT_MARGIN_LEFT)
+            if space_for_another_line and word_fits_in_one_line:
+                # line break
+                offset_x = TEXT_MARGIN_LEFT
+                offset_y += TEXT_LINE_HEIGHT
+                break
+            # word split
+            if space_for_another_line:
+                split = '-'
+                splitw = DASH
+            else:
+                split = '...'
+                splitw = ELLIPSIS
+            # find span that fits
+            for index in range(len(word) - 1, 0, -1):
+                letter = word[index]
+                width -= ui.display.text_width(letter, font)
+                if offset_x + width + splitw < OFFSET_X_MAX:
+                    break
+            else:
+                index = 0
+            span = word[:index]
+            # render word span
+            ui.display.text(offset_x, offset_y, span, font, fg, bg)
+            ui.display.text(offset_x + width, offset_y, split, ui.BOLD, ui.GREY, bg)
+            # line break
+            if not space_for_another_line:
+                return
+            offset_x = TEXT_MARGIN_LEFT
+            offset_y += TEXT_LINE_HEIGHT
+            # continue with the rest
+            word = word[index:]
+            width = ui.display.text_width(word, font)
+
+        # render word
+        ui.display.text(offset_x, offset_y, word, font, fg, bg)
+        offset_x += width
+        offset_x += SPACE
+
+        # line break
+        if new_lines:
+            if not offset_y < OFFSET_Y_MAX:
+                ui.display.text(offset_x, offset_y, '...', ui.BOLD, ui.GREY, bg)
+                return
+            offset_x = TEXT_MARGIN_LEFT
+            offset_y += TEXT_LINE_HEIGHT
 
 
 class Text(ui.Widget):
-
-    def __init__(self, header_text, header_icon, *content, icon_color=ui.ORANGE_ICON, max_lines=None):
+    def __init__(self,
+                 header_text: str,
+                 header_icon: bytes,
+                 *content: list,
+                 new_lines: bool = True,
+                 max_lines: int = TEXT_MAX_LINES,
+                 icon_color: int = ui.ORANGE_ICON):
         self.header_text = header_text
         self.header_icon = header_icon
-        self.icon_color = icon_color
         self.content = content
+        self.new_lines = new_lines
         self.max_lines = max_lines
+        self.icon_color = icon_color
 
     def render(self):
-        offset_x = TEXT_MARGIN_LEFT
-        offset_y = TEXT_LINE_HEIGHT + TEXT_HEADER_HEIGHT
-        style = ui.NORMAL
-        fg = ui.FG
-        bg = ui.BG
         ui.header(self.header_text, self.header_icon, ui.TITLE_GREY, ui.BG, self.icon_color)
-
-        line = 1
-        for item in self.content:
-            if isinstance(item, str):
-                if self.max_lines is not None and line >= self.max_lines:
-                    ui.display.text(offset_x, offset_y, item + '...', style, fg, bg)
-                    break
-                else:
-                    ui.display.text(offset_x, offset_y, item, style, fg, bg)
-                offset_y += TEXT_LINE_HEIGHT
-                line += 1
-            elif item == ui.MONO or item == ui.NORMAL or item == ui.BOLD:
-                style = item
-            else:
-                fg = item
+        render_words(self.content, self.new_lines, self.max_lines)