app_debug_panel_ui :: () {
  if !app.show_debug_panel then return;
  using ImGui;
  
  SetNextWindowSize(imgui_scale(Vector2.{500, 400}), .FirstUseEver);
  
  push_imgui_window("Debug Panel", p_open=*app.show_debug_panel);

  style := GetStyle();
  io := GetIO();
  
  Spacing();

  SeparatorText("Machine");
  Text("Machine name: %", app.machine_name);
  SameLine();
  if SmallButton("Copy##machine_name") {
    clipboard_set_text(app.machine_name);
    toast_show(.Success, "Copied %", app.machine_name);
  }
#if USING_WINDOWS {
  Text("Running as administrator: %", app.is_admin);
  Text("Large pages: %", ifx app.large_pages_allowed then "available" else "unavailable");
}
  Spacing();

  frame_time := 1000.0 / io.Framerate;
  SeparatorText("Performance Metrics");
  Text("% fps | % ms", FF(io.Framerate, 1), FF(frame_time, 3));
  Text("Time to first frame = % ms", FF(perf.time_to_first_frame_ms, 1));
  Checkbox("Frame Times window", *app.show_frame_time_graph);
  ButtonTooltip(to_string(toggle_frame_times_hotkey));
  Checkbox("Command Line window", *app.show_help_panel);
  ButtonTooltip("The command-line options; mcap --help opens it");
  Spacing();

  SeparatorText("Memory Usage");
  Text("Working set: % (peak: %)", format_bytes(perf.memory_usage.working_set), format_bytes(perf.memory_usage.peak_working_set));
  Text("Virtual memory: % (peak: %)", format_bytes(perf.memory_usage.virtual_memory), format_bytes(perf.memory_usage.peak_virtual_memory));
  #if DEBUG {  if Button("Clear Unused Pages") { os_clear_unused_pages(); }  }
  Spacing();
  
  SeparatorText("Fonts");  
  ShowFontSelector("Font Selector");
  
  if DragFloat("FontSizeBase", *style.FontSizeBase, 0.2, 8, 64, "%.0f", .AlwaysClamp) {
    style._NextFrameFontSizeBase = style.FontSizeBase; // #hack as of ImGui v1.92.7
  }
  if IsItemDeactivatedAfterEdit()  app_save_user_settings_file_and_toast("font size");

  // This is how we adjust the font size in user-mode!
  DragFloat("FontScaleMain", *style.FontScaleMain, DEFAULT_FONT_SCALE_INCREMENT, FONT_SCALE_MIN, FONT_SCALE_MAX, flags = .AlwaysClamp);
  if IsItemDeactivatedAfterEdit()  app_save_user_settings_file_and_toast("font size");
  Text("FontScaleDpi: %", style.FontScaleDpi); // should adjust automatically.
  Text("Graphics Backend: %", perf.backend);
  if perf.adapter_name.count > 0 then Text("Adapter: % (%)", perf.adapter_name, ifx perf.renderer_is_software then "software" else "hardware");
#if USING_WINDOWS {
  Text("Startup device (%): % ms", ifx perf.started_on_warp then "WARP" else "hardware", FF(perf.startup_device_ms, 1));
  Text("Startup swap chain: % ms", FF(perf.startup_swap_chain_ms, 1));
  if perf.started_on_warp {
    if perf.hw_device_ready_ms > 0 {
      Text("Hardware device: created in % ms", FF(perf.hw_device_create_ms, 1));
      Text("Hardware device: ready % ms after launch", FF(perf.hw_device_ready_ms, 1));
      Text("Renderer swap: % ms", FF(perf.hw_swap_ms, 1));
    } else {
      Text("Hardware device: pending");
    }
  }
}

  Spacing();
  SeparatorText("Theme");
  current := app_theme_current();
  Text("Current theme: %1%2", ifx current then current.name else "(none)", ifx app_theme.dirty then " *" else "");
  if Button("Open Theme Editor")  app.show_style_editor = true;
  ButtonTooltip(to_string(toggle_style_editor_hotkey));

  Spacing();
  SeparatorText("Settings");
  settings_path := app_user_settings_path();
  if Button("Open settings.config") {
    if !file_exists(settings_path)  app_save_user_settings_file();
    app_open_config_file(settings_path);
  }
  ButtonTooltip(settings_path);
  TextColored(app_theme.palette.dim, "Applied when saved; the window size at the next start.");
  if Button("Reset Layout")  imgui_reset_layout_requested = true;
  ButtonTooltip(tprint("Overwrites % with the default layout built into the app. (%)", to_string(io.IniFilename), to_string(reset_layout_hotkey)));

#if USING_SDL {
  sdlv := SDL_GetVersion();
  sdlr := SDL_GetRevision();

  Text("SDL version: %, revision: %\n", sdlv, to_string(sdlr));
}

  Spacing();
}

app_frame_times_ui :: () {
  if !app.show_frame_time_graph  return;

  ImGui.SetNextWindowSize(imgui_scale(Vector2.{420, 160}), .FirstUseEver);

  push_imgui_window("Frame Times", .NoScrollbar | .NoScrollWithMouse, p_open=*app.show_frame_time_graph);
  frame_time_graph();
}

// The command-line options, opened by mcap -h or --help, or from the Debug Panel. Keep in step with
// the Command line table in README.md.
app_help_panel_ui :: () {
  if !app.show_help_panel  return;
  using ImGui;

  SetNextWindowSize(imgui_scale(Vector2.{760, 560}), .FirstUseEver);
  if app.help_panel_focus { SetNextWindowFocus(); app.help_panel_focus = false; }
  push_imgui_window("Command Line", p_open=*app.show_help_panel);

  Text("% % [FILE] [options]", APP_NAME, VERSION);
  SameLine();
  if SmallButton("Copy") {
    builder: String_Builder;
    builder.allocator = temp;
    for APP_COMMAND_LINE_OPTIONS  print_to_builder(*builder, "%\t%\n", it.option, it.text);
    clipboard_set_text(builder_to_string(*builder,, temp));
    toast_show(.Success, "Copied the command-line options");
  }
  TextColored(app_theme.palette.dim, "-import, -scan, -segment, -stats and -erase still open the window, to show their progress. README.md has the details.");
  Spacing();

  if BeginTable("options", 2, .Borders | .RowBg | .SizingStretchProp | .ScrollY) {
    TableSetupColumn("Option", .WidthFixed);
    TableSetupColumn("What it does", .WidthStretch);
    TableSetupScrollFreeze(0, 1);
    TableHeadersRow();
    for APP_COMMAND_LINE_OPTIONS {
      TableNextRow();
      TableNextColumn();
      TextUnformatted(it.option);
      TableNextColumn();
      TextWrapped("%", it.text);
    }
    EndTable();
  }
}

Command_Line_Option :: struct { option: string; text: string; }

APP_COMMAND_LINE_OPTIONS :: Command_Line_Option.[
  .{"FILE (first)",              "Opens FILE: an .mcap, image or video. With mcap already running, it opens in view mode beside it."},
  .{"-open-import DEST",         "With FILE: imports it into the library folder DEST as its Import button does, then exits: 0 once the library has it (imported, or there already), else 1."},
  .{"-library FOLDER",           "Shows the .mcap files in FOLDER (and its folders) instead of D:\\McapIndex\\mcap."},
  .{"-import SOURCE DEST",       "Imports SOURCE, a folder or a single file, into the library folder DEST, as the Import window does, then exits: 0, or 1 if any file failed."},
  .{"-search QUERY",             "Starts with QUERY in the search box."},
  .{"-scan",                     "Scans the library (the chosen OCR model, and labels when the label model is up) once it has loaded, then exits: 0, or 1 if any capture failed."},
  .{"-segment",                  "Segments the images not yet segmented in the library folders set to segment, then exits: 0, or 1 if any image failed."},
  .{"-stats",                    "Logs the Stats window's numbers once the catalog has loaded, then exits; with -search, for the matches."},
  .{"-erase WHAT",               "Erases ocr, labels, segments or all from every file in the library, then exits (for testing)."},
  .{"-record SECONDS",           "Records the screen under the cursor that long (no overlay), puts it in the library, then exits: 0, or 1 if it failed."},
  .{"-record-region X Y W H",    "With -record: records that region instead."},
  .{"-record-quit",              "With -record: quits while still recording, to check the recording is kept."},
  .{"-record-ui-visible",        "With -record: leaves the border and toolbar in screenshots, to look at them."},
  .{"-cold",                     "Loads the library as on a cold start (its files dropped from the system's file cache first). With -stats, a startup benchmark."},
  .{"-no-catalog-cache",         "Reads every capture from its file, as without the catalog cache (for measuring); the cache is still written."},
  .{"-catalog-threads N",        "Loads the catalog on N threads instead of all the background group's (for measuring)."},
  .{"-allow-multiple-instances", "Runs beside another copy instead of bringing that one forward."},
  .{"-headless",                 "No message boxes: a failure is logged and the app exits with 1."},
  .{"run_tests",                 "Runs the test suites (debug builds); with -headless, exits with 0 if all passed."},
  .{"-version",                  "Prints the version, then exits."},
  .{"-h, --help",                "Opens this window."},
];

frame_time_graph :: () {
  using ImGui;

  frames := perf.frame_times;
  newest := count(frames);
  first  := newest;
  covered: float = 0;
  while first > 0 && covered < 1.0 {
    first -= 1;
    covered += frames[first].delta;
  }

  max_ms := FRAME_BUDGET_MS;
  for first..newest-1  max_ms = max(max_ms, frames[it].work * 1000);

  top_label := tprint("%", FF(max_ms, 1));
  gutter    := imgui_text_size(top_label).x + GetStyle().ItemInnerSpacing.x;
  origin    := GetCursorScreenPos();
  width     := GetContentRegionAvail().x;
  height    := max(GetContentRegionAvail().y, imgui_scale(FRAME_TIME_GRAPH_MIN_HEIGHT));
  Dummy(.{width, height});

  plot_min := Vector2.{origin.x + gutter, origin.y};
  plot_max := Vector2.{origin.x + width,  origin.y + height};
  plot_w   := plot_max.x - plot_min.x;
  if plot_w <= 0  return;

  draw := GetWindowDrawList();
  draw.AddRectFilled(draw, plot_min, plot_max, GetColorU32(.FrameBg));

  bars := newest - first;
  if bars > 0 {
    bar_w := plot_w / cast(float) bars;
    gap: float = xx ifx bar_w >= 3 then 1 else 0;
    for first..newest-1 {
      ms := frames[it].work * 1000;
      x0 := plot_min.x + cast(float) (it - first) * bar_w;
      y0 := plot_max.y - min(ms / max_ms, 1.0) * height;
      draw.AddRectFilled(draw, .{x0, y0}, .{x0 + bar_w - gap, plot_max.y}, GetColorU32(frame_time_color(ms)));
    }
  }

  font_size := GetFontSize();
  frame_time_graph_y_label(draw, plot_min.x, plot_min.y, top_label);
  frame_time_graph_y_label(draw, plot_min.x, plot_max.y - font_size, "0");

  if max_ms > FRAME_BUDGET_MS {
    budget_y := plot_max.y - (FRAME_BUDGET_MS / max_ms) * height;
    draw.AddLine(draw, .{plot_min.x, budget_y}, .{plot_max.x, budget_y}, GetColorU32(.TextDisabled));
    
    label_y := budget_y - font_size * 0.5;
    if label_y > plot_min.y + font_size && label_y < plot_max.y - 2 * font_size {
      frame_time_graph_y_label(draw, plot_min.x, label_y, tprint("%", FF(FRAME_BUDGET_MS, 1)));
    }
  }

  if newest > 0  frame_time_graph_live_value(draw, plot_min, plot_max, frames[newest - 1].work * 1000);
}

frame_time_graph_live_value :: (draw: *ImGui.ImDrawList, plot_min: Vector2, plot_max: Vector2, ms: float) {
  using ImGui;
  push_imgui_font(header_font, scale=FRAME_TIME_LIVE_VALUE_SCALE);

  text := tprint("% ms", FF(ms, 2));
  size := imgui_text_size(text);
  pad  := GetStyle().FramePadding;

  pos := Vector2.{plot_max.x - pad.x - size.x, plot_min.y + pad.y};
  draw.AddText(draw, pos, GetColorU32(.Text, alpha_mul=FRAME_TIME_LIVE_VALUE_ALPHA), text);
}

// Right-aligned against the plot's left edge.
frame_time_graph_y_label :: (draw: *ImGui.ImDrawList, plot_left: float, y: float, text: string) {
  x := plot_left - ImGui.GetStyle().ItemInnerSpacing.x - imgui_text_size(text).x;
  draw.AddText(draw, .{x, y}, ImGui.GetColorU32(.Text), text);
}

// At or under FRAME_TIME_GREEN_MS is fully green, blending to orange at the budget; over it is red.
frame_time_color :: (ms: float) -> Vector4 {
  if ms > FRAME_BUDGET_MS  return app_theme.palette.error;
  t := clamp((ms - FRAME_TIME_GREEN_MS) / (FRAME_BUDGET_MS - FRAME_TIME_GREEN_MS), 0.0, 1.0);
  return lerp(app_theme.palette.success, app_theme.palette.warning, t);
}

FRAME_BUDGET_MS         : float : 1000.0 / 60.0;
FRAME_TIME_GREEN_MS     : float : 1.0;
FRAME_TIME_GRAPH_MIN_HEIGHT : float : 40.0;
FRAME_TIME_LIVE_VALUE_SCALE : float : 2.0;   // of the base font size, in the bold header font
FRAME_TIME_LIVE_VALUE_ALPHA : float : 0.6;