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Refactor ImGui editor layout and scrolling logic for improved precision and consistency.

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This commit is contained in:
Kyle Isom
2026-01-11 15:34:56 -08:00
parent 4c402f5ef3
commit 6eb240a0c4
2 changed files with 119 additions and 122 deletions
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215
ImGuiRenderer.cc
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@@ -94,8 +94,17 @@ ImGuiRenderer::Draw(Editor &ed)
ImGui::SetNextWindowScroll(ImVec2(target_x, target_y));
}
// Reserve space for status bar at bottom
ImGui::BeginChild("scroll", ImVec2(0, -ImGui::GetFrameHeightWithSpacing()), false,
// Reserve space for status bar at bottom.
// We calculate a height that is an exact multiple of the line height
// to avoid partial lines and "scroll past end" jitter.
float total_avail_h = ImGui::GetContentRegionAvail().y;
float wanted_bar_h = ImGui::GetFrameHeight();
float child_h_plan = std::max(0.0f, std::floor((total_avail_h - wanted_bar_h) / row_h) * row_h);
float real_bar_h = total_avail_h - child_h_plan;
ImGui::PushStyleVar(ImGuiStyleVar_WindowPadding, ImVec2(0, 0));
ImGui::PushStyleVar(ImGuiStyleVar_ItemSpacing, ImVec2(0, 0));
ImGui::BeginChild("scroll", ImVec2(0, child_h_plan), false,
ImGuiWindowFlags_HorizontalScrollbar | ImGuiWindowFlags_NoScrollWithMouse);
// Get child window position and scroll for click handling
@@ -138,90 +147,6 @@ ImGuiRenderer::Draw(Editor &ed)
}
prev_buf_rowoffs = buf_rowoffs;
prev_buf_coloffs = buf_coloffs;
// Synchronize cursor and scrolling.
// Ensure the cursor is visible, but avoid aggressive centering so that
// the same lines remain visible until the cursor actually goes off-screen.
{
// Compute visible row range using the child window height
float child_h = ImGui::GetWindowHeight();
long first_row = static_cast<long>(scroll_y / row_h);
long vis_rows = static_cast<long>(child_h / row_h);
if (vis_rows < 1)
vis_rows = 1;
long last_row = first_row + vis_rows - 1;
long cyr = static_cast<long>(cy);
if (cyr < first_row) {
// Scroll just enough to bring the cursor line to the top
float target = static_cast<float>(cyr) * row_h;
if (target < 0.f)
target = 0.f;
float max_y = ImGui::GetScrollMaxY();
if (max_y >= 0.f && target > max_y)
target = max_y;
ImGui::SetScrollY(target);
scroll_y = ImGui::GetScrollY();
first_row = static_cast<long>(scroll_y / row_h);
last_row = first_row + vis_rows - 1;
} else if (cyr > last_row) {
// Scroll just enough to bring the cursor line to the bottom
long new_first = cyr - vis_rows + 1;
if (new_first < 0)
new_first = 0;
float target = static_cast<float>(new_first) * row_h;
float max_y = ImGui::GetScrollMaxY();
if (target < 0.f)
target = 0.f;
if (max_y >= 0.f && target > max_y)
target = max_y;
ImGui::SetScrollY(target);
scroll_y = ImGui::GetScrollY();
first_row = static_cast<long>(scroll_y / row_h);
last_row = first_row + vis_rows - 1;
}
// Horizontal scroll: ensure cursor column is visible
float child_w = ImGui::GetWindowWidth();
long vis_cols = static_cast<long>(child_w / space_w);
if (vis_cols < 1)
vis_cols = 1;
long first_col = static_cast<long>(scroll_x / space_w);
long last_col = first_col + vis_cols - 1;
// Compute cursor's rendered X position (accounting for tabs)
std::size_t cursor_rx = 0;
if (cy < lines.size()) {
std::string cur_line = static_cast<std::string>(lines[cy]);
const std::size_t tabw = 8;
for (std::size_t i = 0; i < cx && i < cur_line.size(); ++i) {
if (cur_line[i] == '\t') {
cursor_rx += tabw - (cursor_rx % tabw);
} else {
cursor_rx += 1;
}
}
}
long cxr = static_cast<long>(cursor_rx);
if (cxr < first_col || cxr > last_col) {
float target_x = static_cast<float>(cxr) * space_w;
// Center horizontally if possible
target_x -= (child_w / 2.0f);
if (target_x < 0.f)
target_x = 0.f;
float max_x = ImGui::GetScrollMaxX();
if (max_x >= 0.f && target_x > max_x)
target_x = max_x;
ImGui::SetScrollX(target_x);
scroll_x = ImGui::GetScrollX();
}
// Phase 3: prefetch visible viewport highlights and warm around in background
if (buf->SyntaxEnabled() && buf->Highlighter() && buf->Highlighter()->HasHighlighter()) {
int fr = static_cast<int>(std::max(0L, first_row));
int rc = static_cast<int>(std::max(1L, vis_rows));
buf->Highlighter()->PrefetchViewport(*buf, fr, rc, buf->Version());
}
}
// Cache current horizontal offset in rendered columns for click handling
const std::size_t coloffs_now = buf->Coloffs();
@@ -489,23 +414,98 @@ ImGuiRenderer::Draw(Editor &ed)
ImGui::GetWindowDrawList()->AddRectFilled(p0, p1, col);
}
}
// Synchronize cursor and scrolling after rendering all lines so content size is known.
{
float child_h_actual = ImGui::GetWindowHeight();
float child_w_actual = ImGui::GetWindowWidth();
float scroll_y_now = ImGui::GetScrollY();
float scroll_x_now = ImGui::GetScrollX();
long first_row = static_cast<long>(scroll_y_now / row_h);
long vis_rows = static_cast<long>(std::round(child_h_actual / row_h));
if (vis_rows < 1)
vis_rows = 1;
long last_row = first_row + vis_rows - 1;
long cyr = static_cast<long>(cy);
if (cyr < first_row) {
float target = static_cast<float>(cyr) * row_h;
if (target < 0.f)
target = 0.f;
float max_y = ImGui::GetScrollMaxY();
if (max_y >= 0.f && target > max_y)
target = max_y;
ImGui::SetScrollY(target);
first_row = static_cast<long>(target / row_h);
last_row = first_row + vis_rows - 1;
} else if (cyr > last_row) {
long new_first = cyr - vis_rows + 1;
if (new_first < 0)
new_first = 0;
float target = static_cast<float>(new_first) * row_h;
float max_y = ImGui::GetScrollMaxY();
if (target < 0.f)
target = 0.f;
if (max_y >= 0.f && target > max_y)
target = max_y;
ImGui::SetScrollY(target);
first_row = static_cast<long>(target / row_h);
last_row = first_row + vis_rows - 1;
}
// Horizontal scroll: ensure cursor column is visible
long vis_cols = static_cast<long>(std::round(child_w_actual / space_w));
if (vis_cols < 1)
vis_cols = 1;
long first_col = static_cast<long>(scroll_x_now / space_w);
long last_col = first_col + vis_cols - 1;
std::size_t cursor_rx = 0;
if (cy < lines.size()) {
std::string cur_line = static_cast<std::string>(lines[cy]);
const std::size_t tabw = 8;
for (std::size_t i = 0; i < cx && i < cur_line.size(); ++i) {
if (cur_line[i] == '\t') {
cursor_rx += tabw - (cursor_rx % tabw);
} else {
cursor_rx += 1;
}
}
}
long cxr = static_cast<long>(cursor_rx);
if (cxr < first_col || cxr > last_col) {
float target_x = static_cast<float>(cxr) * space_w;
target_x -= (child_w_actual / 2.0f);
if (target_x < 0.f)
target_x = 0.f;
float max_x = ImGui::GetScrollMaxX();
if (max_x >= 0.f && target_x > max_x)
target_x = max_x;
ImGui::SetScrollX(target_x);
}
if (buf->SyntaxEnabled() && buf->Highlighter() && buf->Highlighter()->HasHighlighter()) {
int fr = static_cast<int>(std::max(0L, first_row));
int rc = static_cast<int>(std::max(1L, vis_rows));
buf->Highlighter()->PrefetchViewport(*buf, fr, rc, buf->Version());
}
}
ImGui::EndChild();
ImGui::PopStyleVar(2); // WindowPadding, ItemSpacing
// Status bar spanning full width
ImGui::Separator();
// Compute full content width and draw a filled background rectangle
// Status bar area starting right after the scroll child
ImVec2 win_pos = ImGui::GetWindowPos();
ImVec2 cr_min = ImGui::GetWindowContentRegionMin();
ImVec2 cr_max = ImGui::GetWindowContentRegionMax();
float x0 = win_pos.x + cr_min.x;
float x1 = win_pos.x + cr_max.x;
ImVec2 cursor = ImGui::GetCursorScreenPos();
float bar_h = ImGui::GetFrameHeight();
ImVec2 p0(x0, cursor.y);
ImVec2 p1(x1, cursor.y + bar_h);
ImVec2 win_sz = ImGui::GetWindowSize();
float x0 = win_pos.x;
float x1 = win_pos.x + win_sz.x;
float y0 = ImGui::GetCursorScreenPos().y;
float bar_h = real_bar_h;
ImVec2 p0(x0, y0);
ImVec2 p1(x1, y0 + bar_h);
ImU32 bg_col = ImGui::GetColorU32(ImGuiCol_HeaderActive);
ImGui::GetWindowDrawList()->AddRectFilled(p0, p1, bg_col);
// If a prompt is active, replace the entire status bar with the prompt text
if (ed.PromptActive()) {
std::string label = ed.PromptLabel();
@@ -591,11 +591,9 @@ ImGuiRenderer::Draw(Editor &ed)
ImVec2 msg_sz = ImGui::CalcTextSize(final_msg.c_str());
ImGui::PushClipRect(ImVec2(p0.x, p0.y), ImVec2(p1.x, p1.y), true);
ImGui::SetCursorScreenPos(ImVec2(left_x, p0.y + (bar_h - msg_sz.y) * 0.5f));
ImGui::SetCursorScreenPos(ImVec2(left_x, y0 + (bar_h - msg_sz.y) * 0.5f));
ImGui::TextUnformatted(final_msg.c_str());
ImGui::PopClipRect();
// Advance cursor to after the bar to keep layout consistent
ImGui::Dummy(ImVec2(x1 - x0, bar_h));
} else {
// Build left text
std::string left;
@@ -671,20 +669,21 @@ ImGuiRenderer::Draw(Editor &ed)
float max_left = std::max(0.0f, right_x - left_x - pad);
if (max_left < left_sz.x && max_left > 10.0f) {
// Render a clipped left using a child region
ImGui::SetCursorScreenPos(ImVec2(left_x, p0.y + (bar_h - left_sz.y) * 0.5f));
ImGui::PushClipRect(ImVec2(left_x, p0.y), ImVec2(right_x - pad, p1.y), true);
ImGui::SetCursorScreenPos(ImVec2(left_x, y0 + (bar_h - left_sz.y) * 0.5f));
ImGui::PushClipRect(ImVec2(left_x, y0), ImVec2(right_x - pad, y0 + bar_h),
true);
ImGui::TextUnformatted(left.c_str());
ImGui::PopClipRect();
}
} else {
// Draw left normally
ImGui::SetCursorScreenPos(ImVec2(left_x, p0.y + (bar_h - left_sz.y) * 0.5f));
ImGui::SetCursorScreenPos(ImVec2(left_x, y0 + (bar_h - left_sz.y) * 0.5f));
ImGui::TextUnformatted(left.c_str());
}
// Draw right
ImGui::SetCursorScreenPos(ImVec2(std::max(right_x, left_x),
p0.y + (bar_h - right_sz.y) * 0.5f));
y0 + (bar_h - right_sz.y) * 0.5f));
ImGui::TextUnformatted(right.c_str());
// Draw middle message centered in remaining space
@@ -696,14 +695,12 @@ ImGuiRenderer::Draw(Editor &ed)
ImVec2 msg_sz = ImGui::CalcTextSize(msg.c_str());
float msg_x = mid_left + std::max(0.0f, (mid_w - msg_sz.x) * 0.5f);
// Clip to middle region
ImGui::PushClipRect(ImVec2(mid_left, p0.y), ImVec2(mid_right, p1.y), true);
ImGui::SetCursorScreenPos(ImVec2(msg_x, p0.y + (bar_h - msg_sz.y) * 0.5f));
ImGui::PushClipRect(ImVec2(mid_left, y0), ImVec2(mid_right, y0 + bar_h), true);
ImGui::SetCursorScreenPos(ImVec2(msg_x, y0 + (bar_h - msg_sz.y) * 0.5f));
ImGui::TextUnformatted(msg.c_str());
ImGui::PopClipRect();
}
}
// Advance cursor to after the bar to keep layout consistent
ImGui::Dummy(ImVec2(x1 - x0, bar_h));
}
}