feat(glfw): adapter and 1 MS/s streaming demo

adapters/glfw/CMakeLists.txt

@@ -0,0 +1,51 @@
+# The GLFW adapter: the reference host for the library. It owns the window, the
+# context and the loop, and translates GLFW's events into plot::input events.
+#
+# Dependency discovery follows the design spec's order: find_package first,
+# pkg-config next, FetchContent only when neither can supply GLFW (the last
+# resort, because it needs the network).
+set(plot_glfw_dep "")
+
+find_package(glfw3 3.3 QUIET)
+if(TARGET glfw)
+  set(plot_glfw_dep glfw)
+elseif(TARGET glfw3::glfw3)
+  set(plot_glfw_dep glfw3::glfw3)
+endif()
+
+if(NOT plot_glfw_dep)
+  find_package(PkgConfig QUIET)
+  if(PkgConfig_FOUND)
+    pkg_check_modules(GLFW_PC QUIET IMPORTED_TARGET glfw3)
+    if(TARGET PkgConfig::GLFW_PC)
+      set(plot_glfw_dep PkgConfig::GLFW_PC)
+    endif()
+  endif()
+endif()
+
+if(NOT plot_glfw_dep)
+  message(STATUS "plot: glfw3 not found via find_package or pkg-config; fetching it")
+  include(FetchContent)
+  set(GLFW_BUILD_DOCS OFF CACHE BOOL "" FORCE)
+  set(GLFW_BUILD_TESTS OFF CACHE BOOL "" FORCE)
+  set(GLFW_BUILD_EXAMPLES OFF CACHE BOOL "" FORCE)
+  set(GLFW_INSTALL OFF CACHE BOOL "" FORCE)
+  FetchContent_Declare(glfw
+    GIT_REPOSITORY https://github.com/glfw/glfw.git
+    GIT_TAG 3.4
+    GIT_SHALLOW TRUE)
+  FetchContent_MakeAvailable(glfw)
+  set(plot_glfw_dep glfw)
+endif()
+
+message(STATUS "plot: GLFW adapter dependency: ${plot_glfw_dep}")
+
+add_library(plot_glfw STATIC glfw_host.cpp)
+add_library(plot::glfw ALIAS plot_glfw)
+# The public include root is `adapters/`, so the header is reached as
+# <glfw/glfw_host.hpp> -- the toolkit's name first, like every other adapter's.
+target_include_directories(plot_glfw PUBLIC "${CMAKE_CURRENT_SOURCE_DIR}/..")
+# GLFW stays PRIVATE: the header forward-declares GLFWwindow and includes no GLFW
+# header, so a consumer of plot::glfw does not inherit the toolkit.
+target_link_libraries(plot_glfw PUBLIC plot::core PRIVATE ${plot_glfw_dep})
+plot_apply_warnings(plot_glfw)

adapters/glfw/glfw_host.cpp

@@ -0,0 +1,346 @@
+#include <glfw/glfw_host.hpp>
+
+// Before GLFW's header, so it does not include <GL/gl.h>: that header's macros
+// (GL_COLOR_BUFFER_BIT and friends) would rewrite `plot::gl`'s enumerators of the
+// same name. The adapter needs GLFW for the window, the context and the events
+// only -- every GL entry point comes from plot::gl::load().
+#define GLFW_INCLUDE_NONE
+#include <GLFW/glfw3.h>
+
+#include <plot/gl/loader.hpp>
+
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+
+namespace plot::glfw {
+namespace {
+
+/// GLFW_MOD_* and `plot::input::Mod` are the same bits, by design: the
+/// controller documents `Mod` as the host-translatable mask. A key event's mask
+/// therefore passes through, and only a pointer or wheel event, whose callbacks
+/// carry no mask, has to ask the window for the current key state.
+static_assert(static_cast<u32>(GLFW_MOD_SHIFT) == static_cast<u32>(input::Mod::Shift));
+static_assert(static_cast<u32>(GLFW_MOD_CONTROL) == static_cast<u32>(input::Mod::Ctrl));
+static_assert(static_cast<u32>(GLFW_MOD_ALT) == static_cast<u32>(input::Mod::Alt));
+static_assert(static_cast<u32>(GLFW_MOD_SUPER) == static_cast<u32>(input::Mod::Super));
+
+u32 mods_now(GLFWwindow* w) noexcept {
+  u32 m = 0;
+  if (glfwGetKey(w, GLFW_KEY_LEFT_SHIFT) == GLFW_PRESS ||
+      glfwGetKey(w, GLFW_KEY_RIGHT_SHIFT) == GLFW_PRESS) {
+    m |= GLFW_MOD_SHIFT;
+  }
+  if (glfwGetKey(w, GLFW_KEY_LEFT_CONTROL) == GLFW_PRESS ||
+      glfwGetKey(w, GLFW_KEY_RIGHT_CONTROL) == GLFW_PRESS) {
+    m |= GLFW_MOD_CONTROL;
+  }
+  if (glfwGetKey(w, GLFW_KEY_LEFT_ALT) == GLFW_PRESS ||
+      glfwGetKey(w, GLFW_KEY_RIGHT_ALT) == GLFW_PRESS) {
+    m |= GLFW_MOD_ALT;
+  }
+  if (glfwGetKey(w, GLFW_KEY_LEFT_SUPER) == GLFW_PRESS ||
+      glfwGetKey(w, GLFW_KEY_RIGHT_SUPER) == GLFW_PRESS) {
+    m |= GLFW_MOD_SUPER;
+  }
+  return m;
+}
+
+bool any_button_down(GLFWwindow* w) noexcept {
+  return glfwGetMouseButton(w, GLFW_MOUSE_BUTTON_LEFT) == GLFW_PRESS ||
+         glfwGetMouseButton(w, GLFW_MOUSE_BUTTON_RIGHT) == GLFW_PRESS ||
+         glfwGetMouseButton(w, GLFW_MOUSE_BUTTON_MIDDLE) == GLFW_PRESS;
+}
+
+/// `glfwGetProcAddress` returns GLFW's `void (*)(void)`, `plot::gl::ProcLoader`
+/// returns `void*`: a function pointer respelled as an object pointer. POSIX
+/// guarantees the two have the same representation, and the bit copy states that
+/// where a `reinterpret_cast` would be merely conditionally supported.
+void* resolve_gl(const char* name) noexcept {
+  GLFWglproc p = glfwGetProcAddress(name);
+  void* out = nullptr;
+  static_assert(sizeof(out) == sizeof(p), "function and object pointers must match");
+  std::memcpy(&out, &p, sizeof(out));
+  return out;
+}
+
+bool fail(Status* st, ErrorCode code, const char* message) noexcept {
+  if (st != nullptr) {
+    st->code = code;
+    st->message = message;
+  }
+  return false;
+}
+
+/// `PLOT_DEMO_EXIT_AFTER_MS` as seconds: 0.0 when unset, unparsable or not
+/// positive, which is "run until the window is closed".
+f64 exit_after_seconds() noexcept {
+  const char* v = std::getenv("PLOT_DEMO_EXIT_AFTER_MS");
+  if (v == nullptr || v[0] == '\0') return 0.0;
+  char* end = nullptr;
+  const f64 ms = std::strtod(v, &end);
+  if (end == v || !(ms > 0.0)) return 0.0;
+  return ms * 1.0e-3;
+}
+
+}  // namespace
+
+Host::Host() noexcept : controller_(plot_) {}
+
+Host::~Host() { close(); }
+
+void Host::close() noexcept {
+  // The renderer's RAII handles call glDelete* from their destructors, so the
+  // context has to be current -- and alive -- when they run.
+  if (renderer_) {
+    if (window_ != nullptr) glfwMakeContextCurrent(window_);
+    renderer_.reset();
+  }
+  if (window_ != nullptr) {
+    glfwDestroyWindow(window_);
+    window_ = nullptr;
+  }
+  glfwMakeContextCurrent(nullptr);
+  glfwTerminate();
+  have_pointer_ = false;
+}
+
+bool Host::run(const RunConfig& cfg, const FrameFn& frame, Status* st) {
+  if (st != nullptr) *st = Status{};
+  close();  // a second run() starts from a clean window
+
+  if (glfwInit() != GLFW_TRUE) {
+    return fail(st, ErrorCode::Unsupported, "glfwInit() failed");
+  }
+
+  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
+  glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
+  glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
+  // Required on macOS 10.7+, ignored elsewhere.
+  glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GLFW_TRUE);
+  // A run with a deadline is the automated path, so it stays off-screen: a
+  // bounded CI run must never flash a window on a real display.
+  const f64 exit_after_s = exit_after_seconds();
+  if (exit_after_s > 0.0) glfwWindowHint(GLFW_VISIBLE, GLFW_FALSE);
+
+  GLFWwindow* w = glfwCreateWindow(cfg.width > 0 ? cfg.width : 1,
+                                   cfg.height > 0 ? cfg.height : 1,
+                                   cfg.title != nullptr ? cfg.title : "plot", nullptr, nullptr);
+  if (w == nullptr) {
+    const char* desc = nullptr;
+    (void)glfwGetError(&desc);
+    std::fprintf(stderr, "plot::glfw: glfwCreateWindow() failed: %s\n",
+                 desc != nullptr ? desc : "no error description");
+    close();
+    return fail(st, ErrorCode::Unsupported,
+                "glfwCreateWindow() failed: no OpenGL 3.3 core context (see stderr)");
+  }
+
+  window_ = w;
+  glfwSetWindowUserPointer(w, this);
+  glfwMakeContextCurrent(w);
+  glfwSwapInterval(cfg.vsync ? 1 : 0);
+  glfwSetCursorPosCallback(w, &Host::cursor_pos_cb);
+  glfwSetMouseButtonCallback(w, &Host::mouse_button_cb);
+  glfwSetScrollCallback(w, &Host::scroll_cb);
+  glfwSetKeyCallback(w, &Host::key_cb);
+  glfwSetFramebufferSizeCallback(w, &Host::framebuffer_size_cb);
+  refresh_sizes();
+
+  if (!plot::gl::load(&resolve_gl)) {
+    close();
+    return fail(st, ErrorCode::Unsupported,
+                "plot::gl::load() failed: the context is missing a required OpenGL 3.3 entry point");
+  }
+
+  renderer_.emplace();
+  if (!renderer_->init(st)) {
+    close();
+    if (st != nullptr && st->code == ErrorCode::Ok) {
+      *st = Status{ErrorCode::GLFailure, "Renderer::init() failed"};
+    }
+    return false;
+  }
+
+  const char* const screenshot = std::getenv("PLOT_DEMO_SCREENSHOT");
+  const f64 start = glfwGetTime();
+  f64 previous = start;
+
+  while (glfwWindowShouldClose(window_) == GLFW_FALSE) {
+    glfwPollEvents();
+    refresh_sizes();
+
+    if (fb_width_ == 0 || fb_height_ == 0) {
+      // Minimised, or a size the compositor reports as zero: nothing to draw
+      // into. Idle briefly rather than spin, so an exit deadline still lands.
+      glfwWaitEventsTimeout(0.05);
+      continue;
+    }
+
+    // The plot's region is the whole window here, which is what the controller
+    // and `begin_frame` must agree on: one rect, in framebuffer pixels, set
+    // before the frame callback runs so it sees the layout it draws into.
+    const Rect viewport{0.0f, 0.0f, static_cast<f32>(fb_width_), static_cast<f32>(fb_height_)};
+    controller_.set_viewport(viewport);  // also Plot::set_viewport, then layout()
+
+    const f64 now = glfwGetTime();
+    const f64 dt = now - previous;
+    previous = now;
+    if (frame) frame(plot_, dt);
+
+    const bool exiting = exit_after_s > 0.0 && (now - start) >= exit_after_s;
+
+    renderer_->begin_frame(fb_width_, fb_height_, viewport);
+    renderer_->draw(plot_);
+    if (exiting && screenshot != nullptr && screenshot[0] != '\0') {
+      Status shot;
+      const bool dumped = renderer_->dump_frame_ppm(screenshot, &shot);
+      std::printf("[glfw] screenshot %s: %s\n", screenshot,
+                  dumped ? "written" : shot.message);
+      std::fflush(stdout);
+    }
+    renderer_->end_frame();
+    glfwSwapBuffers(window_);
+
+    if (exiting) break;
+  }
+  return true;
+}
+
+void Host::set_title(const char* title) noexcept {
+  if (window_ != nullptr) glfwSetWindowTitle(window_, title != nullptr ? title : "");
+}
+
+void Host::refresh_sizes() noexcept {
+  if (window_ == nullptr) return;
+  int fw = 0;
+  int fh = 0;
+  int ww = 0;
+  int wh = 0;
+  glfwGetFramebufferSize(window_, &fw, &fh);
+  glfwGetWindowSize(window_, &ww, &wh);
+  float sx = 1.0f;
+  float sy = 1.0f;
+  glfwGetWindowContentScale(window_, &sx, &sy);
+  content_scale_x_ = sx;
+  content_scale_y_ = sy;
+  if (fw > 0) fb_width_ = static_cast<u32>(fw);
+  if (fh > 0) fb_height_ = static_cast<u32>(fh);
+  if (ww > 0 && fw > 0) fb_scale_x_ = static_cast<f32>(fw) / static_cast<f32>(ww);
+  if (wh > 0 && fh > 0) fb_scale_y_ = static_cast<f32>(fh) / static_cast<f32>(wh);
+}
+
+// ------------------------------------------------------------------ events
+
+Host* Host::from(GLFWwindow* w) noexcept {
+  return w != nullptr ? static_cast<Host*>(glfwGetWindowUserPointer(w)) : nullptr;
+}
+
+void Host::cursor_pos_cb(GLFWwindow* w, double x, double y) {
+  if (Host* h = from(w)) h->on_cursor_pos(x, y);
+}
+
+void Host::mouse_button_cb(GLFWwindow* w, int button, int action, int mods) {
+  if (Host* h = from(w)) h->on_mouse_button(button, action, mods);
+}
+
+void Host::scroll_cb(GLFWwindow* w, double dx, double dy) {
+  if (Host* h = from(w)) h->on_scroll(dx, dy);
+}
+
+void Host::key_cb(GLFWwindow* w, int key, int scancode, int action, int mods) {
+  (void)scancode;
+  if (Host* h = from(w)) h->on_key(key, action, mods);
+}
+
+void Host::framebuffer_size_cb(GLFWwindow* w, int width, int height) {
+  (void)width;
+  (void)height;
+  if (Host* h = from(w)) h->refresh_sizes();
+}
+
+void Host::on_cursor_pos(f64 wx, f64 wy) noexcept {
+  // Window coordinates -> framebuffer pixels: the same translation the viewport
+  // and every other Rect here use, so a gesture lands where it was aimed.
+  const f32 x = static_cast<f32>(wx) * fb_scale_x_;
+  const f32 y = static_cast<f32>(wy) * fb_scale_y_;
+  input::PointerEvent e;
+  e.x = x;
+  e.y = y;
+  if (have_pointer_) {
+    e.dx = x - last_pointer_x_;
+    e.dy = y - last_pointer_y_;
+  }
+  last_pointer_x_ = x;
+  last_pointer_y_ = y;
+  have_pointer_ = true;
+  e.mods = mods_now(window_);
+  e.down = any_button_down(window_);
+  controller_.on_pointer(e);
+}
+
+void Host::on_mouse_button(int button, int action, int mods) noexcept {
+  input::Button b;
+  switch (button) {
+    case GLFW_MOUSE_BUTTON_LEFT: b = input::Button::Left; break;
+    case GLFW_MOUSE_BUTTON_MIDDLE: b = input::Button::Middle; break;
+    case GLFW_MOUSE_BUTTON_RIGHT: b = input::Button::Right; break;
+    default: return;  // the controller has no gesture for the auxiliary buttons
+  }
+  double wx = 0.0;
+  double wy = 0.0;
+  glfwGetCursorPos(window_, &wx, &wy);
+  input::PointerEvent e;
+  e.x = static_cast<f32>(wx) * fb_scale_x_;
+  e.y = static_cast<f32>(wy) * fb_scale_y_;
+  // The press/release is also a pointer sample: the next move's delta starts
+  // here, or a drag's first motion would include the jump to the click.
+  last_pointer_x_ = e.x;
+  last_pointer_y_ = e.y;
+  have_pointer_ = true;
+  e.button = b;
+  e.mods = static_cast<u32>(mods);
+  e.pressed = action == GLFW_PRESS;
+  e.released = action == GLFW_RELEASE;
+  e.down = any_button_down(window_);
+  controller_.on_pointer(e);
+}
+
+void Host::on_scroll(f64 dx, f64 dy) noexcept {
+  double wx = 0.0;
+  double wy = 0.0;
+  glfwGetCursorPos(window_, &wx, &wy);
+  input::WheelEvent e;
+  e.x = static_cast<f32>(wx) * fb_scale_x_;
+  e.y = static_cast<f32>(wy) * fb_scale_y_;
+  e.dx = static_cast<f32>(dx);
+  e.dy = static_cast<f32>(dy);  // GLFW's positive y (scroll up) is the zoom-in sign
+  e.mods = mods_now(window_);
+  controller_.on_wheel(e);
+}
+
+void Host::on_key(int key, int action, int mods) noexcept {
+  int mapped = 0;
+  switch (key) {
+    // The controller zooms on '+', which on most layouts is shift+'='; the '='
+    // key is mapped to it as well, so both spellings zoom in.
+    case GLFW_KEY_EQUAL:
+    case GLFW_KEY_KP_ADD: mapped = input::kKeyZoomIn; break;
+    case GLFW_KEY_MINUS:
+    case GLFW_KEY_KP_SUBTRACT: mapped = input::kKeyZoomOut; break;
+    case GLFW_KEY_F: mapped = input::kKeyFit; break;
+    case GLFW_KEY_ESCAPE:
+      if (action == GLFW_PRESS) glfwSetWindowShouldClose(window_, GLFW_TRUE);
+      return;
+    default: return;
+  }
+  input::KeyEvent e;
+  e.key = mapped;
+  e.mods = static_cast<u32>(mods);
+  // GLFW reports auto-repeat as its own action; a held key keeps acting, exactly
+  // as holding the key on a keyboard does.
+  e.down = action != GLFW_RELEASE;
+  controller_.on_key(e);
+}
+
+}  // namespace plot::glfw

adapters/glfw/glfw_host.hpp

@@ -0,0 +1,154 @@
+#pragma once
+
+#include <functional>
+#include <optional>
+
+#include <plot/core/rect.hpp>
+#include <plot/core/status.hpp>
+#include <plot/core/types.hpp>
+#include <plot/input/controller.hpp>
+#include <plot/plot/plot.hpp>
+#include <plot/render/renderer.hpp>
+
+/// GLFW's window type. Forward-declared on purpose: this header is
+/// self-contained and needs no GLFW include directory, so a consumer of the
+/// adapter does not inherit the toolkit's headers (and their `<GL/gl.h>`, whose
+/// macros would rewrite this library's enumerators).
+struct GLFWwindow;
+
+namespace plot::glfw {
+
+/// What `Host::run()` opens the window with.
+struct RunConfig {
+  int width = 1280;
+  int height = 720;
+  const char* title = "plot";
+  bool vsync = true;
+};
+
+/// One frame of application code, called by `Host::run()` after the viewport is
+/// set and before the frame is staged, so it is where data is refreshed.
+/// `dt` is the wall time since the previous call, in seconds.
+using FrameFn = std::function<void(plot::Plot&, f64 dt)>;
+
+/// The reference host: owns the GLFW window and its OpenGL 3.3 core context, the
+/// GL entry points, the `Renderer`, the `Plot`, the `input::Controller` and the
+/// frame loop, so nothing above it names GLFW or GL.
+///
+/// Per-frame sequence, in this order:
+///
+///   poll events -> controller.set_viewport(framebuffer-pixel rect) ->
+///   frame(plot, dt) -> begin_frame -> draw -> [screenshot] -> end_frame ->
+///   swap buffers
+///
+/// Two pixel spaces meet here and must not be confused. GLFW reports the cursor
+/// and the window in *window* coordinates, while the framebuffer -- what
+/// `begin_frame` takes and what every `Rect` in this library speaks -- can be
+/// larger under a fractional or HiDPI scale, so `glfwGetFramebufferSize()` and
+/// `glfwGetWindowSize()` disagree. The host calls `begin_frame` with the
+/// framebuffer size and scales every pointer coordinate by the ratio
+/// `framebuffer / window`, so a gesture lands on the pixels the plot was laid out
+/// in. On an unscaled display the ratio is 1.0 and nothing changes.
+///
+/// Headless smoke mode, read once per `run()`:
+///
+///   `PLOT_DEMO_EXIT_AFTER_MS=<n>`  stop the loop after n ms and return
+///                                  (default 0: run until the window is closed)
+///   `PLOT_DEMO_SCREENSHOT=<path>`  on that final frame, write it with
+///                                  `Renderer::dump_frame_ppm()` before the swap
+///
+/// That is what lets a CI run a GUI library under `xvfb-run`: no display access
+/// and no screen capture, just a PPM on disk.
+///
+/// A run with a deadline is that automated path, so its window is created hidden
+/// (`GLFW_VISIBLE` false): an automated run must not flash a window on whatever
+/// display it lands on. It also means the loop is not throttled by a display
+/// refresh, so the frame times it reports are the CPU's, not a vblank's. A run
+/// without a deadline shows its window, as an interactive application must.
+///
+/// Not thread-safe, and confined to the thread that runs `run()`.
+class Host {
+ public:
+  Host() noexcept;
+  ~Host();
+  Host(const Host&) = delete;
+  Host& operator=(const Host&) = delete;
+
+  /// Opens the window, makes a 3.3 core context current, resolves the GL entry
+  /// points and initialises the renderer, then runs the loop until the window is
+  /// closed or the exit deadline passes. Returns false with `st` filled in when
+  /// GLFW, the context or `Renderer::init()` fails; a failed run leaves nothing
+  /// open.
+  ///
+  /// On success the window *stays open*, so a caller can stop and join whatever
+  /// feeds the plot before the GL resources go away: `close()` (or the
+  /// destructor) releases the renderer, the context and the window, in that
+  /// order, on this thread. Calling `run()` again reopens the window and keeps
+  /// the plot.
+  bool run(const RunConfig& cfg, const FrameFn& frame, Status* st = nullptr);
+
+  /// Releases the renderer and the window. Idempotent, and safe on a host that
+  /// never ran.
+  void close() noexcept;
+
+  /// The plot the frame callback populates. Valid for the host's whole life.
+  Plot& plot() noexcept { return plot_; }
+  /// The gesture controller the host feeds. Valid for the host's whole life.
+  input::Controller& controller() noexcept { return controller_; }
+
+  /// The renderer, or null while no window is open. Valid from inside the frame
+  /// callback and after a successful `run()`; `close()` releases it.
+  Renderer* renderer() noexcept { return renderer_ ? &*renderer_ : nullptr; }
+
+  /// Retitles the open window -- from the frame callback, for a live
+  /// samples/second and frame-time readout. A no-op while no window is open.
+  void set_title(const char* title) noexcept;
+
+  /// Framebuffer pixels per window pixel, one ratio per axis, as of the last
+  /// event or frame. 1.0 on an unscaled display.
+  f32 framebuffer_scale_x() const noexcept { return fb_scale_x_; }
+  f32 framebuffer_scale_y() const noexcept { return fb_scale_y_; }
+  /// The window's content scale, one per axis, as of the last frame.
+  f32 content_scale_x() const noexcept { return content_scale_x_; }
+  f32 content_scale_y() const noexcept { return content_scale_y_; }
+
+ private:
+  /// Reads the framebuffer and window sizes and the content scale, refreshing
+  /// the window -> framebuffer ratios the pointer translation uses.
+  void refresh_sizes() noexcept;
+
+  /// Callbacks find their host through GLFW's per-window user pointer.
+  static Host* from(GLFWwindow* w) noexcept;
+  static void cursor_pos_cb(GLFWwindow* w, double x, double y);
+  static void mouse_button_cb(GLFWwindow* w, int button, int action, int mods);
+  static void scroll_cb(GLFWwindow* w, double dx, double dy);
+  static void key_cb(GLFWwindow* w, int key, int scancode, int action, int mods);
+  static void framebuffer_size_cb(GLFWwindow* w, int width, int height);
+
+  void on_cursor_pos(f64 wx, f64 wy) noexcept;
+  void on_mouse_button(int button, int action, int mods) noexcept;
+  void on_scroll(f64 dx, f64 dy) noexcept;
+  void on_key(int key, int action, int mods) noexcept;
+
+  Plot plot_;
+  input::Controller controller_;  ///< forwards its viewport to `plot_`
+  std::optional<Renderer> renderer_;
+  GLFWwindow* window_ = nullptr;
+
+  u32 fb_width_ = 0;   ///< framebuffer size of the last refresh_sizes()
+  u32 fb_height_ = 0;
+  /// Framebuffer pixels per window pixel. Taken from the two sizes GLFW reports
+  /// rather than from the content scale, which under a fractional scale does not
+  /// round back to the framebuffer size.
+  f32 fb_scale_x_ = 1.0f;
+  f32 fb_scale_y_ = 1.0f;
+  f32 content_scale_x_ = 1.0f;
+  f32 content_scale_y_ = 1.0f;
+  /// Last pointer position in framebuffer pixels: the deltas the controller pans
+  /// with are the movements since the previous event, which GLFW does not report.
+  f32 last_pointer_x_ = 0.0f;
+  f32 last_pointer_y_ = 0.0f;
+  bool have_pointer_ = false;
+};
+
+}  // namespace plot::glfw